SnowConvert: Transact DDLs¶
Translation reference for all the DDL statements that are preceded by the CREATE word.
Index¶
Applies to
[x] SQL Server
[x] Azure Synapse Analytics
Warning
Currently, Create Index statement is not being converted but it is being parsed. Also, if your source code has Create index statements, these are going to be accounted for in the Assessment Report.
Example of Create Index
CREATE INDEX my_index_name ON my_table (column1, column2);
Note
Due to architectural reasons, Snowflake does not support indexes so, SnowConvert will remove all the code related to the creation of indexes. Snowflake automatically creates micro-partitions for every table that help speed up the performance of DML operations, the user does not have to worry about creating or managing these micro-partitions.
Usually, this is enough to have a very good query performance however, there are ways to improve it by creating data clustering keys. Snowflake’s official page provides more information about micro-partitions and data clustering.
Materialized View¶
Applies to
[x] Azure Synapse Analytics
Description ¶
In Snowconvert, Materialized Views are transformed into Snowflake Dynamic Tables. To properly configure Dynamic Tables, two essential parameters must be defined: TARGET_LAG and WAREHOUSE. If these parameters are left unspecified in the configuration options, Snowconvert will default to preassigned values during the conversion, as demonstrated in the example below.
For more information on Materialized Views, click here.
For details on the necessary parameters for Dynamic Tables, click here.
Sample Source Patterns¶
SqlServer
CREATE MATERIALIZED VIEW sales_total
AS
SELECT SUM(amount) AS total_sales
FROM sales;
Snowflake
CREATE OR REPLACE DYNAMIC TABLE sales_total
--** SSC-FDM-0031 - DYNAMIC TABLE REQUIRED PARAMETERS SET BY DEFAULT **
TARGET_LAG='1 day'
WAREHOUSE=UPDATE_DUMMY_WAREHOUSE
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"oracle"}}'
AS
SELECT SUM(amount) AS total_sales
FROM
sales;
Known Issues¶
No known errors detected at this time.
Procedures¶
Applies to
[x] SQL Server
[x] Azure Synapse Analytics
Note
Some parts in the output code are omitted for clarity reasons.
1. CREATE PROCEDURE Translation¶
Snowflake CREATE PROCEDURE is defined in SQL Syntax whereas its inner statements are defined in JavaScript.
Source Code:
-- Additional Params: -t JavaScript
CREATE PROCEDURE HumanResources.uspGetAllEmployees
@FirstName NVARCHAR(50),
@Age INT
AS
-- TSQL Statements and queries...
GO
Translated Code:
CREATE OR REPLACE PROCEDURE HumanResources.uspGetAllEmployees (FIRSTNAME STRING, AGE INT)
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
$$;
Parameter’s DATA TYPE¶
Parameters data types are being translated to Snowflake equivalent. See also Data Types.
EXEC helper¶
In order to be able to run statements from a procedure in the SnowFlake environment, these statements have to be preprocessed and adapted to reflect their execution in several variables that are specific to the source language.
SnowConvert automatically translates the supported statements and makes use of an EXEC helper. This helper provides access and update capabilities to many variables that simulate how the execution of these statements would be in their native environment.
For instance, you may see that in the migrated procedures, there is a block of code that is always added. We are going to explain the basic structure of this code in the next section. Please keep in mind that we are always evaluating and searching for new and improved ways to streamline the transformations and any helper that we require.
Structure¶
The basic structure of the EXEC helper is as follows:
Variable declaration section: Here, we declare the different variables or objects that will contain values associated with the execution of the statements inside the procedure. This includes values such as the number of rows affected by a statement, or even the result set itself.
fixBind function declaration: This is an auxiliary function used to fix binds when they are of Date type.
EXEC function declaration: This is the main EXEC helper function. It receives the statement to execute, the array of binds (basically the variables or parameters that may be modified by the execution and require data permanence throughout the execution of the procedure), the noCatch flag that determines if the ERROR_HANDLERS must be used, and the catchFunction function for executing custom code when there’s an exception in the execution of the statement. The body of the EXEC function is very straightforward; execute the statement and store every valuable data produced by its execution, all inside an error handling block.
ERROR VARS: The EXEC catch block sets up a list of error variables such as
MESSAGE_TEXT,SQLCODE,SQLSTATE,PROC_NAMEandERROR_LINEthat could be used to retrieve values from user defined functions, in order to emulate the SQL Server ERROR_LINE, ERROR_MESSAGE, ERROR_NUMBER, ERROR_PROCEDURE and ERROR_STATE built in functions behavour. After all of these variables are set with one value, theUPDATE_ERROR_VARSuser defined function, will be in charge of update some environment variables with the error values, in order to have access to them in the SQL scope.
Code¶
The following code block represents the EXEC helper inside a procedure:
var _RS, ROW_COUNT, _ROWS, MESSAGE_TEXT, SQLCODE = 0, SQLSTATE = '00000', ERROR_HANDLERS, NUM_ROWS_AFFECTED, INTO;
var fixBind = function (arg) {
arg = arg == undefined ? null : arg instanceof Date ? arg.toISOString() : arg;
return arg;
};
var fetch = (count,rows,stmt) => (count && rows.next() && Array.apply(null,Array(stmt.getColumnCount())).map((_,i) => rows.getColumnValue(i + 1))) || [];
var EXEC = (stmt,binds = [],noCatch = false) => {
binds = binds ? binds.map(fixBind) : binds;
for(var stmt of stmt.split(";").filter((_) => _)) {
try {
_RS = snowflake.createStatement({
sqlText : stmt,
binds : binds
});
_ROWS = _RS.execute();
ROW_COUNT = _RS.getRowCount();
NUM_ROWS_AFFECTED = _RS.getNumRowsAffected();
return {
THEN : (action) => !SQLCODE && action(fetch(_ROWS))
};
} catch(error) {
let rStack = new RegExp('At .*, line (\\d+) position (\\d+)');
let stackLine = error.stackTraceTxt.match(rStack) || [0,-1];
MESSAGE_TEXT = error.message.toString();
SQLCODE = error.code.toString();
SQLSTATE = error.state.toString();
snowflake.execute({sqlText: `SELECT UPDATE_ERROR_VARS_UDF(?,?,?,?,?)`,binds: [stackLine[1], SQLCODE, SQLSTATE, MESSAGE_TEXT, PROC_NAME]});
throw error;
}
}
};
Simple EXEC example
This is a simple example of an EXEC call inside a Stored Procedure
Source Code
-- Additional Params: -t JavaScript
CREATE PROCEDURE dbo.EXEC_EXAMPLE_1
AS
EXECUTE('SELECT 1 AS Message');
GO
-- =============================================
-- Example to execute the stored procedure
-- =============================================
EXECUTE dbo.EXEC_EXAMPLE_1
GO
Expected code
CREATE OR REPLACE PROCEDURE dbo.EXEC_EXAMPLE_1 ()
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// REGION SnowConvert Helpers Code
var _RS, ROW_COUNT, _ROWS, MESSAGE_TEXT, SQLCODE = 0, SQLSTATE = '00000', OBJECT_SCHEMA_NAME = 'dbo', ERROR_HANDLERS, NUM_ROWS_AFFECTED, PROC_NAME = arguments.callee.name, DOLLAR_DOLLAR = '$' + '$';
function* sqlsplit(sql) {
var part = '';
var ismark = () => sql[i] == '$' && sql[i + 1] == '$';
for(var i = 0;i < sql.length;i++) {
if (sql[i] == ';') {
yield part + sql[i];
part = '';
} else if (ismark()) {
part += sql[i++] + sql[i++];
while ( i < sql.length && !ismark() ) {
part += sql[i++];
}
part += sql[i] + sql[i++];
} else part += sql[i];
}
if (part.trim().length) yield part;
};
var formatDate = (arg) => (new Date(arg - (arg.getTimezoneOffset() * 60000))).toISOString().slice(0,-1);
var fixBind = function (arg) {
arg = arg == undefined ? null : arg instanceof Date ? formatDate(arg) : arg;
return arg;
};
var EXEC = (stmt,binds = [],severity = "16",noCatch = false) => {
binds = binds ? binds.map(fixBind) : binds;
for(var stmt of sqlsplit(stmt)) {
try {
_RS = snowflake.createStatement({
sqlText : stmt,
binds : binds
});
_ROWS = _RS.execute();
ROW_COUNT = _RS.getRowCount();
NUM_ROWS_AFFECTED = _RS.getNumRowsAffected();
return {
THEN : (action) => !SQLCODE && action(fetch(_ROWS))
};
} catch(error) {
let rStack = new RegExp('At .*, line (\\d+) position (\\d+)');
let stackLine = error.stackTraceTxt.match(rStack) || [0,-1];
MESSAGE_TEXT = error.message.toString();
SQLCODE = error.code.toString();
SQLSTATE = error.state.toString();
snowflake.execute({
sqlText : `SELECT UPDATE_ERROR_VARS_UDF(?,?,?,?,?,?)`,
binds : [stackLine[1],SQLCODE,SQLSTATE,MESSAGE_TEXT,PROC_NAME,severity]
});
throw error;
}
}
};
// END REGION
EXEC(`SELECT 1 AS Message;`);
$$;
EXEC within a Store Procedure with a parameter
In this example, the EXEC command is inside a Stored Procedure and receives a parameter value
Source Code
-- Additional Params: -t JavaScript
CREATE PROCEDURE dbo.EXEC_EXAMPLE_2
@p1 varchar(50) = N''
AS
EXEC ('SELECT ' + @p1);
GO
-- =============================================
-- Example to execute the stored procedure
-- =============================================
EXECUTE dbo.EXEC_EXAMPLE_2 N'''Hello World!'''
GO
Expected Code
CREATE OR REPLACE PROCEDURE dbo.EXEC_EXAMPLE_2 (P1 STRING DEFAULT '')
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
EXEC(`SELECT
${P1};`);
$$;
EXEC invoking a Store Procedure with a parameter
In this example, the EXEC invokes another Stored Procedure and pass adds a parameter
Source Code
-- Additional Params: -t JavaScript
CREATE PROCEDURE dbo.EXEC_EXAMPLE_3
@p1 varchar(50) = N''
AS
EXEC EXEC_EXAMPLE_2 @p1
GO
-- =============================================
-- Example to execute the stored procedure
-- =============================================
EXECUTE dbo.EXEC_EXAMPLE_3 N'''Hello World!'''
GO
Expected Code
CREATE OR REPLACE PROCEDURE dbo.EXEC_EXAMPLE_3 (P1 STRING DEFAULT '')
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
EXEC(`CALL EXEC_EXAMPLE_2(?)`,[P1]);
$$;
Parameters with Default Value.¶
In SqlServer, there can be parameters with a default value in case these are not specified when a procedure is being called.
For example
CREATE PROCEDURE PROC_WITH_DEFAULT_PARAMS1
@PARAM1 INT = 0, @PARAM2 INT = 0, @PARAM3 INT = 0, @PARAM4 INT = 0
AS
BEGIN
.
.
.
END
In Snowflake is translated to
CREATE OR REPLACE PROCEDURE PROC_WITH_DEFAULT_PARAMS1(param1 int default 0, param2 int default 0, param3 int default 0, param4 int default 0)
RETURNS TABLE()
LANGUAGE SQL
EXECUTE AS CALLER
AS
$$
.
.
.
$$;
CALL PROC_WITH_DEFAULT_PARAMS1(param2 => 10, param4 => 15);
CURSOR helper¶
CREATE OR REPLACE PROCEDURE PROC1()
RETURNS STRING
LANGUAGE JAVASCRIPT
EXECUTE AS CALLER
AS
$$
var CURSOR = function (stmt, binds) {
var statementObj, result_set, total_rows, isOpen = false, self = this, row_count;
this.CURRENT = new Object;
var fetch = (count,rows,stmt) => (count && rows.next() && Array.apply(null,Array(stmt.getColumnCount())).map((_,i) => rows.getColumnValue(i + 1))) || [];
var fixBind = function (arg) {
arg = arg == undefined ? null : arg instanceof Date ? formatDate(arg) : arg;
return arg;
};
this.OPEN = function(openParameters) {
if (result_set == undefined) {
try {
if (openParameters) binds = openParameters;
if (binds instanceof Function) binds = binds();
var finalBinds = binds && binds.map(fixBind);
var finalStmt = stmt instanceof Function ? stmt() : stmt;
statementObj = snowflake.createStatement({
sqlText : finalStmt,
binds : finalBinds
});
result_set = statementObj.execute();
total_rows = statementObj.getRowCount();
isOpen = true;
row_count = 0;
} catch(error) {
RAISE(error.code,"error",error.message);
}
else {
isOpen = true;
}
}
return this;
};
this.CURSOR_ROWS = function () {
return total_rows;
};
this.FETCH_STATUS = function() {
if(total_rows > row_count)
return 0;
else
return -1;
};
this.FETCH_NEXT = function() {
self.res = [];
if (isOpen) {
self.res = fetch(total_rows,result_set,statementObj);
if (self.res)
row_count++;
}
return self.res && self.res.length > 0;
};
this.INTO = function () {
return self.res;
};
this.CLOSE = function () {
isOpen = false;
};
this.DEALLOCATE = function() {
this.CURRENT = row_count = result_set_table = total_rows = result_set = statementObj = self = undefined;
};
};
var COL1, COL2;
var sql_stmt = ``;
let c = new CURSOR(`SELECT COL1, COL2 FROM TABLE1;`,() => []);
c.OPEN();
c.FETCH_NEXT();
[COL1, COL2] = c.INTO();
while ( c.FETCH_STATUS()) {
sql_stmt = `INSERT INTO TABLE2 (COL1, COL2) VALUES (` + COL1+ `, ` + COL2 + `)`;
snowflake.createStatement({
sqlText : sql_stmt
}).execute();
}
c.CLOSE();
c.DEALLOCATE();
return 'sucess';
$$;
Insert Into EXEC Helper¶
The Insert into Exec helper generates a function called Insert insertIntoTemporaryTable(sql). This function will allow the transformation for INSERT INTO TABLE_NAME EXEC(...) from TSQL to Snowflake to imitate the behavior from the original statement by inserting it’s data into a temporary table and then re-adding it into the original Insert.
For more information on how the code for this statement is modified look at the section for Insert Into Exec
Note
This Generated code for the INSERT INTO EXEC, may present performance issues when handling EXECUTE statements containing multiple queries inside.
function insertIntoTemporaryTable(sql) {
var table = "SnowConvertPivotTemporaryTable";
return EXEC('CREATE OR REPLACE TEMPORARY TABLE ${table} AS ${sql}');
}
insertIntoTemporaryTable(`${DBTABLES}`)
EXEC(`INSERT INTO MYDB.PUBLIC.T_Table SELECT * FROM MYDB.PUBLIC.SnowConvertPivotTemporaryTable`);
EXEC(`DROP TABLE SnowConvertPivotTemporaryTable`)
LIKE Helper¶
In case that a like expression is found in a procedure, for example
CREATE PROCEDURE ProcedureLike @VariableValue VARCHAR(50) AS
BEGIN
IF @VariableValue like '%c%'
BEGIN
Select AValue from ATable;
END;
END;
Since the inside of the procedure is transformed to javascript, the like expression will throw an error. In order to avoid and keep the functionality, a function is added at the start of the procedure if a like expression is found.
function LIKE(expr,pattern,esc,cs) {
function fixPattern(pattern,esc) {
const specials = '/.*+?|(){}[]\\'.split('');
var newPattern = "";
var fix = (c) => specials.includes(c) ? '\\' + c : c;
for(var i = 0;i < pattern.length;i++) {
var c = pattern[i];
if (c === esc) {
newPattern += pattern[i + 1]
i++
} else if (c === '%') {
newPattern += ".*?"
} else if (c === '_') {
newPattern += "."
} else if (c === '[' || ']') {
newPattern += c
} else newPattern += fix(c)
}
return newPattern;
}
return new RegExp(`^${fixPattern(pattern,esc)}$`,cs ? '' : 'i').exec(expr) != null;
}
With this function, we can replicate the functionality of the like expression of sql. Let’s see the diferent cases that it can be used
-- Additional Params: -t JavaScript
CREATE PROCEDURE ProcedureLike @VariableValue VARCHAR(50) AS
BEGIN
IF @VariableValue like '%c%'
BEGIN
Select AValue from ATable;
END;
IF @VariableValue not like '%c%'
BEGIN
Select BValue from BTable;
END;
IF @VariableValue like '%c!%%' escape '!'
BEGIN
Select CValue from CTable;
END;
END;
In the last code, there is a normal like a not like, and a like with escape. The transformation will be
CREATE OR REPLACE PROCEDURE ProcedureLike (VARIABLEVALUE STRING)
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
if (LIKE(VARIABLEVALUE,`%c%`)) {
{
EXEC(` Select
AValue
from
ATable`);
}
}
if (!LIKE(VARIABLEVALUE,`%c%`)) {
{
EXEC(` Select
BValue
from
BTable`);
}
}
if (LIKE(VARIABLEVALUE,`%c!%%`,`!`)) {
{
EXEC(` Select
CValue
from
CTable`);
}
}
$$;
Note that the likes are transformed to function calls
LIKE(VARIABLEVALUE,`%c%`)
!LIKE(VARIABLEVALUE,`%c%`)
LIKE(VARIABLEVALUE,`%c!%%`,`!`)
The parameters that the function LIKE receive are the followings:
The expression that is being evaluated.
The pattern of comparison
If it is present, the escape character, this is an optional parameter.
Select Helper¶
Generates a function called SELECT when a scalar value has to be set to a variable
-- Additional Params: -t JavaScript
CREATE PROCEDURE MAX_EMPLOYEE_ID
AS
BEGIN
DECLARE @VARIABLE INT
SET @VARIABLE = (SELECT MAX(EMPLOYEE_ID) FROM EMPLOYEES);
RETURN @VARIABLE
END;
In this case, it will generate the following code with the SELECT helper
CREATE OR REPLACE PROCEDURE MAX_EMPLOYEE_ID ()
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
let VARIABLE;
VARIABLE = SELECT(` MAX(EMPLOYEE_ID) FROM
EMPLOYEES`);
return VARIABLE;
$$;
The SELECT helper could be used as well to insert into a local value a retrieved value from a query. The helper was designed specifically to support the same behavour of the SQL Server SELECT @local_variable. The args parameter, represents each operation applied to all of the local variables inside the select. See also SELECT @Variable. For example:
-- Additional Params: -t JavaScript
CREATE PROCEDURE [PROCEDURE1] AS
DECLARE @VAR1 int;
DECLARE @VAR2 int;
select @VAR1 = col1 + col2, @VAR2 += col1 from table1;
GO
In this case the variable assignments will be translated to JavaScript lambdas in order to emulate the SQL Server behavior.
CREATE OR REPLACE PROCEDURE PROCEDURE1 ()
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
let VAR1;
let VAR2;
SELECT(` col1 + col2,
col1
from
table1`,[],(value) => VAR1 = value,(value) => VAR2 += value);
$$;
RAISERROR Helper¶
This helper is generated when there exists usages of a RAISERROR call in the source code. Example:
var RAISERROR = (message,severity,state) => {
snowflake.execute({
sqlText : `SELECT UPDATE_ERROR_VARS_UDF(?,?,?)`,
binds : [message,severity,state]
});
var msg = `Message: ${message}, Level: ${severity}, State: ${state}`;
throw msg;
};
The RAISERROR executes the UPDATE_ERROR_VARS_UDF in order to store the value of the error message, severity and state as environment variables, in case they need to be used by calling any of the ERROR built in functions. Finally, the error message is thrown with the same format as SQL Server does.
Identity Function Helper¶
This helper is generated whenever the Identity Fuction is used on a Select Into inside a procedure.
var IdentityHelper = (seed,increment) => {
var sequenceString = "`CREATE OR REPLACE SEQUENCE SnowConvert_Temp_Seq START = ${seed} INCREMENT = ${increment}`";
return EXEC(sequenceString);
The parameters for this helper are the same as the original function, it is created in order to generate a sequence to mimic the identity function behavior in TSQL, the changes to the original code are:
An additional method call to the IdentityHelper function using the same parameters found in the source code.
And call to the IDENTITY_UDF a function design to get the next value in the sequence.
IdentityHelper(1,1)
EXEC(`CREATE TABLE PUBLIC.department_table3 AS SELECT IDENTITY_UDF() /*** MSC-WARNING - MSCEWI1046 - 'identity' FUNCTION MAPPED TO 'IDENTITY_UDF', FUNCTIONAL EQUIVALENCE VERIFICATION PENDING ***/ as Primary_Rank
from PUBLIC.department_table`);
Just like in the TSQL if no parameters are given (1,1) will be the default values.
CALL Procedure Helper¶
This helper is generated whenever there is a call to what previously was a user defined function, but is now a procedure as a result of the translation process.
var CALL = (sql,binds = [],...args) => {
EXEC("CALL " + sql,binds);
_ROWS.next();
return (_ROWS.getColumnValue(1))[0];
};
The purpose of this helper is to encapsulate the logic required for calling procedures as if they were functions.
Please keep in mind that this functionality is limited, since procedures cannot be invoked within queries such as SELECT.
Example of use, assuming that FooSelfAssign(@PAR INT) was translated to a procedure:
// Input code
DECLARE @VAR1 INT = FooSelfAssign(1);
DECLARE @VAR4 INT = FooSelfAssign(FooSelfAssign(FooSelfAssign(FooSelfAssign(4))));
// Output code
let VAR1 = CALL(`FooSelfAssign(1)`)
let VAR4 = CALL(`FooSelfAssign(?)`,[CALL(`FooSelfAssign(?)`,[CALL(`FooSelfAssign(?)`,[CALL(`FooSelfAssign(4)`)])])]);
Note that the translation for VAR1 is very straightforward, but for VAR4, the outmost CALL contains a list with the rest of the CALLs, as bindings.
Each successive CALL is translated to a binding, if it’s contained within another CALL.
2. Variables¶
DECLARE @Variable¶
Source Code
DECLARE @product_list VARCHAR(MAX) = ' ';
DECLARE @Variable1 AS VARCHAR(100), @Variable2 AS VARCHAR(100);
Translated Code
let PRODUCT_LIST = ` `;
let VARIABLE1;
let VARIABLE2;
DECLARE @Variable Table¶
In this case, the DECLARE is used to declare a variable table, let’s see an example.
-- Additional Params: -t JavaScript
CREATE PROCEDURE PROC1
AS
BEGIN
DECLARE @VariableNameTable TABLE
(
[Col1] INT NOT NULL,
[Col2] INT NOT NULL
);
INSERT INTO @VariableNameTable Values(111,222);
Select * from @VariableNameTable;
END
Exec PROC1;
If we execute that code in Sql Server, we will get the following result
Now, let’s see the transformation in Snowflake
CREATE OR REPLACE PROCEDURE PROC1 ()
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
{
EXEC(`CREATE OR REPLACE TEMPORARY TABLE T_VariableNameTable
(
Col1 INT NOT NULL,
Col2 INT NOT NULL
)`);
EXEC(`INSERT INTO T_VariableNameTable Values(111,222)`);
EXEC(`Select
*
from
T_VariableNameTable`);
}
EXEC(`CALL PROC1()`);
$$;
Note that from the lines 61 to 67 are the results of those statements inside the procedure.
The Declare Variable Table is turned into a Temporary Table. Note that the name, which that in the name the character @ was replaced for T_.
If we execute that code in Snowflake, we will not get any result. it will display just null. That’s because that last Select is now in the EXEC helper. So, how do we know that the table is there?
Since it was created as a temporary table inside the Procedure in an EXEC, we can do a Select to that table outside of the Procedure.
Select * from PUBLIC.T_VariableNameTable;
If we execute that statement, we will get the following result
SET @Variable¶
For now, the Set Variable is transformed depending on the expression that is has on the right side.
If the expression has a transformation, it will be transformed to it’s JavaScript equivalent.
Example
-- Additional Params: -t JavaScript
CREATE PROCEDURE PROC1
AS
BEGIN
SET @product_list2 = '';
SET @product_list = '';
SET @var1 += '';
SET @var2 &= '';
SET @var3 ^= '';
SET @var4 |= '';
SET @var5 /= '';
SET @var6 %= '';
SET @var7 *= '';
SET @var8 -= '';
SET @ProviderStatement = 'SELECT * FROM TABLE1
WHERE COL1 = '+@PARAM1+ ' AND COL2 = ' + @LOCALVAR1;
SET @NotSupported = functionValue(a,b,c);
END
Translated Code
CREATE OR REPLACE PROCEDURE PROC1 ()
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
PRODUCT_LIST2 = ``;
PRODUCT_LIST = ``;
VAR1 += ``;
VAR2 &= ``;
VAR3 ^= ``;
VAR4 |= ``;
VAR5 /= ``;
VAR6 %= ``;
VAR7 *= ``;
VAR8 -= ``;
PROVIDERSTATEMENT = `SELECT
*
FROM
TABLE1
WHERE
COL1 = ${PARAM1}
AND COL2 = ${LOCALVAR1};`;
NOTSUPPORTED = SELECT(` !!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'functionValue' NODE ***/!!!
functionValue(a, b, c)`);
$$;
As you can see in the example, the value of the variable NOTSUPPORTED is commented since it is not being transformed for the time being. Note that means that the transformation is not completed yet.
Other kinds of sets are commented, for example the following
-- Additional Params: -t JavaScript
CREATE PROCEDURE PROC1
AS
BEGIN
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
;
SET NOCOUNT ON
;
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
;
SET NOCOUNT OFF
;
END
Translated Code
CREATE OR REPLACE PROCEDURE PROC1 ()
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
/*** SSC-EWI-0040 - THE STATEMENT IS NOT SUPPORTED IN SNOWFLAKE ***/
/*SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED*/
;
/*** SSC-EWI-0040 - THE STATEMENT IS NOT SUPPORTED IN SNOWFLAKE ***/
/*SET NOCOUNT ON*/
;
/*** SSC-EWI-0040 - THE STATEMENT IS NOT SUPPORTED IN SNOWFLAKE ***/
/*SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED*/
;
/*** SSC-EWI-0040 - THE STATEMENT IS NOT SUPPORTED IN SNOWFLAKE ***/
/*SET NOCOUNT OFF*/
;
$$;
SELECT @Variable¶
For now, the SELECT @variable is being transformed into a simple select, removing the variable assignations, and keeping the expressions at the right side of the operator. The assignment operations of the local variables in the select, will be replaced with arrow functions that represent the same behavour of the operation being did during the local variable assignment in SQL Server.
Input¶
-- Additional Params: -t JavaScript
CREATE PROCEDURE PROC1 AS
DECLARE @VAR1 int;
DECLARE @VAR2 int;
SELECT @VAR1 = COL1 + COL2, @VAR2 = COL3 FROM TABLE1;
GO
Output¶
CREATE OR REPLACE PROCEDURE PROC1 ()
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
let VAR1;
let VAR2;
SELECT(` COL1 + COL2,
COL3
FROM
TABLE1`,[],(value) => VAR1 = value,(value) => VAR2 = value);
$$;
3. Statements translation¶
SELECT¶
Basic form¶
The basic SELECT form does not have bindings, so the translation implies the creation of a call to the EXEC helper function, with one parameter.
For example:
-- Source code:
SELECT * FROM DEMO_TABLE_1;
// Translated code:
EXEC(`SELECT * FROM DEMO_TABLE_1`);
IF¶
Source Code
IF Conditional_Expression
-- SQL Statement
ELSE IF Conditiona_Expression2
-- SQL Statement
ELSE
-- SQL Statement
Translated Code
if (Conditional_Expression) {
// SQL Statement
} else if (Conditional_Expression2) {
// SQL Statement
} else{
// SQL Statement
}
WHILE¶
Source Code
WHILE ( Conditional_Expression )
BEGIN
-- SQL STATEMENTS
END;
Translated Code
while ( Conditional_Expression )
{
// SQL STATEMENTS
}
EXEC / EXECUTE¶
Source code
-- Execute simple statement
Exec('Select 1');
-- Execute statement using Dynamic Sql
Exec('Select ' + @par1 + ' from [db].[t1]');
-- Execute Procedure with parameter
EXEC db.sp2 'Create proc [db].[p3] AS', @par1, 1
Translated Code
-- Execute simple statement
EXEC(`Select 1`);
-- Execute statement using Dynamic Sql
EXEC(`Select ${PAR1} from MYDB.db.t1`);
-- Execute Procedure with parameter
EXEC(`CALL db.sp2(/*** SSC-EWI-0038 - THIS STATEMENT MAY BE A DYNAMIC SQL THAT COULD NOT BE RECOGNIZED AND CONVERTED ***/
'Select * from MYDB.db.t1', ?, 1, Default)`,[PAR1]);
THROW¶
The transformation for THROW ensures that the catch block that receives the error has access to the information specified in the original statement.
For instance:
-- Case 1
THROW
-- Case 2
THROW 123, 'The error message', 1
-- Case 3
THROW @var1, @var2, @var3
Will be transformed to:
// Case 1
throw {};
// Case 2
throw { code: 123, message: "The error message", status: 1 };
// Case 3
throw { code: VAR1, message: VAR2, status: VAR3 };
RAISERROR¶
SQL Server RAISERROR function is not supported in Snowflake. SnowConvert identifies all the usages in order to generate a helper that emulates the original behavour. Example:
From¶
-- Additional Params: -t JavaScript
CREATE OR ALTER PROCEDURE RAISERRORTEST AS
BEGIN
DECLARE @MessageTXT VARCHAR = 'ERROR MESSAGE';
RAISERROR (N'E_INVALIDARG', 16, 1);
RAISERROR ('Diagram does not exist or you do not have permission.', 16, 1);
RAISERROR(@MessageTXT, 16, 1);
END
GO
To¶
CREATE OR REPLACE PROCEDURE RAISERRORTEST ()
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
let MESSAGETXT = `ERROR MESSAGE`;
RAISERROR("E_INVALIDARG","16","1");
RAISERROR("Diagram does not exist or you do not have permission.","16","1");
RAISERROR(MESSAGETXT,"16","1");
$$;
BREAK/CONTINUE¶
The break/continue transformation, ensures flow of the code to be stopped or continue with another block.
For instance:
-- Additional Params: -t JavaScript
CREATE PROCEDURE ProcSample
AS
BEGIN
IF @@ROWCOUNT > 0
Continue;
ELSE
BREAK;
END
Will be transformed to:
CREATE OR REPLACE PROCEDURE ProcSample ()
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
if (ROW_COUNT > 0) {
continue;
} else {
break;
}
$$;
INSERT INTO EXEC¶
The code is modify slightly due to the INSERT INTO [Table] EXEC(...) Statement not being supported in Snowflake this allows us to replicate the behavior by adding a few lines of code:
The first line added is a call to the
insertIntoTemporaryTableto where the extracted code from the argument inside theEXEC, this will Insert the result set into a Temporary table. For more information on the function check the Insert Into EXEC Helper section.The Insert’s Exec is removed from the code and a query retrieving the results of the EXEC from the temporary table.
SELECT * FROM MYDB.PUBLIC.SnowConvertPivotTemporaryTable
The last line added is a DROP TABLE statement for the Temporary Table added.
DROP TABLE SnowConvertPivotTemporaryTable
Source Code:
INSERT INTO #Table1
EXEC ('SELECT
Table1.ID
FROM Population');
INSERT INTO #Table1
EXEC (@DBTables);
Translated Code:
insertIntoTemporaryTable(`SELECT Table1.ID FROM MYDB.PUBLIC.Population)
EXEC(`INSERT INTO MYDB.PUBLIC.T_Table1 SELECT * FROM MYDB.PUBLIC.SnowConvertPivotTemporaryTable`);
EXEC(`DROP TABLE SnowConvertPivotTemporaryTable`)
insertIntoTemporaryTable(`${DBTABLES}`)
EXEC(`INSERT INTO MYDB.PUBLIC.T_Table1 SELECT * FROM MYDB.PUBLIC.SnowConvertPivotTemporaryTable`);
EXEC(`DROP TABLE SnowConvertPivotTemporaryTable`)
BEGIN TRANSACTION¶
BEGIN TRANSACTION is transformed to Snowflake’s BEGIN command, and inserted into an EXEC helper call.
The helper is in charge of actually executing the resulting BEGIN.
Example:
-- Input code
BEGIN TRAN @transaction_name;
// Output code
EXEC(`BEGIN`, []);
COMMIT TRANSACTION¶
COMMIT TRANSACTION is transformed to Snowflake’s COMMIT command, and inserted into an EXEC helper call.
The helper is in charge of actually executing the resulting COMMIT.
Example:
-- Input code
COMMIT TRAN @transaction_name;
// Output code
EXEC(`COMMIT`, []);
ROLLBACK TRANSACTION¶
ROLLBACK TRANSACTION is transformed to Snowflake’s ROLLBACK command, and inserted into an EXEC helper call.
The helper is in charge of actually executing the resulting ROLLBACK .
Example:
-- Input code
ROLLBACK TRAN @transaction_name;
// Output code
EXEC(`ROLLBACK`, []);
WAITFOR DELAY¶
WAITFOR DELAY clause is transformed to Snowflake’s SYSTEM$WAIT function. The time_to_pass parameter of the DELAY is transformed to seconds, for usage as a parameter in the SYSTEM$WAIT function.
The other variants of the WAITFOR clause are not supported in Snowflake, and are therefore marked with the corresponding message.
Example:
-- Input code
1) WAITFOR DELAY '02:00';
2) WAITFOR TIME '13:30';
3) WAITFOR (RECEIVE TOP (1)
@dh = conversation_handle,
@mt = message_type_name,
@body = message_body
FROM [eqe]), TIMEOUT 5000;
// Output code
1) EXEC(`SYSTEM$WAIT(120)`,[]);
2) /*** SSC-EWI-0040 - THE STATEMENT IS NOT SUPPORTED IN SNOWFLAKE ***/
/*WAITFOR TIME '13:30'*/
;
3) /*** SSC-EWI-0040 - THE STATEMENT IS NOT SUPPORTED IN SNOWFLAKE ***/
/*WAITFOR (RECEIVE TOP (1)
@dh = conversation_handle,
@mt = message_type_name,
@body = message_body
FROM [eqe]), TIMEOUT 5000*/
;
3. Cursors¶
Since CURSORS are not supported in Snowflake, SnowConvert maps their functionality to a JavaScript helper that emulates the original behavior in the target platform. Example:
Input:¶
-- Additional Params: -t JavaScript
CREATE PROCEDURE [procCursorHelper] AS
DECLARE vendor_cursor CURSOR FOR
SELECT VendorID, Name
FROM Purchasing.Vendor
WHERE PreferredVendorStatus = 1
ORDER BY VendorID;
GO
Output:¶
CREATE OR REPLACE PROCEDURE procCursorHelper ()
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
var VENDOR_CURSOR = new CURSOR(`SELECT
VendorID,
Name
FROM
Purchasing.Vendor
WHERE
PreferredVendorStatus = 1
ORDER BY VendorID`,[],false);
$$;
DECLARE CURSOR¶
For now, the Declare Cursor is just being commented.
Source Code
DECLARE myCursor1 CURSOR FOR SELECT COL1 FROM TABLE1
Translated Code
let myCursor1 = new CURSOR(`SELECT COL1 FROM TABLE1`,() => []);
OPEN¶
Source Code
OPEN myCursor1
OPEN GLOBAL myCursor2
Translated Code
myCursor1.OPEN();
myCursor2.OPEN()
FETCH¶
Source Code
DECLARE @VALUE1 INT
FETCH NEXT FROM myCursor1 into @VALUE1
Translated Code
var VALUE1;
myCursor1.FETCH_NEXT();
VALUE1 = myCursor1.INTO();
CLOSE¶
Source Code
CLOSE myCursor1
CLOSE GLOBAL myCursor2
Translated Code
myCursor1.CLOSE()
myCursor2.CLOSE()
DEALLOCATE¶
Source Code
DEALLOCATE myCursor1
DEALLOCATE GLOBAL myCursor2
Translated Code
myCursor1.DEALLOCATE()
myCursor2.DEALLOCATE()
@@FETCH_STATUS¶
Source Code
@@FETCH_STATUS
Translated Code
myCursor1.FETCH_STATUS()
@@CURSOR_ROWS¶
Source Code
@@CURSOR_ROWS
Translated Code
myCursor1.FETCH_STATUS()
4. Expressions¶
Binary Operations¶
Source Code
SET @var1 = 1 + 1;
SET @var1 = 1 - 1;
SET @var1 = 1 / 1;
SET @var1 = 1 * 1;
SET @var1 = 1 OR 1;
SET @var1 = 1 AND 1;
Translated Code
VAR1 = 1 + 1;
VAR1 = 1 - 1;
VAR1 = 1 / 1;
VAR1 = 1 * 1;
VAR1 = 1 || 1;
VAR1 = 1 && 1;
Conditionals¶
Source Code
@var1 > 0
@var1 = 0
@var1 < 0
@var1 <> 0
Translated Code
VAR1 > 0
VAR1 = 0
VAR1 < 0
VAR1 != 0
IN Predicate¶
NULL Predicate¶
Source Code
@var1 is null
@var2 is not null
Translated Code
VAR1 == null
VAR2 != null
5. Labels and Goto¶
Labels have not the same behavior in JavaScript as SQL Server has. To simulate the behavior, they are being transformed to functions . Its usage is being replaced with a call of the generated function that contains all the logic of the label. Example:
Source Code¶
-- Additional Params: -t JavaScript
CREATE PROCEDURE [procWithLabels]
AS
SUCCESS_EXIT:
SET @ErrorStatus = 0
RETURN @ErrorStatus
ERROR_EXIT:
RETURN @ErrorStatus
Translated Code¶
CREATE OR REPLACE PROCEDURE procWithLabels ()
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
SUCCESS_EXIT();
ERROR_EXIT();
function SUCCESS_EXIT() {
ERRORSTATUS = 0;
return ERRORSTATUS;
}
function ERROR_EXIT() {
return ERRORSTATUS;
}
$$;
As you see in the example above, the function declarations that were the labels in the source code, will be put at the end of the code in order to make it cleaner.
GOTO is another command that does not exist in JavaScript. To simulate its behavour, their usages are being transformed to calls to the function (label) that is referenced, preceded by a return statement. Example:
Source Code¶
-- Additional Params: -t JavaScript
CREATE PROCEDURE [procWithLabels]
AS
DECLARE @ErrorStatus int = 0;
IF @ErrorStatus <> 0 GOTO ERROR_EXIT
SUCCESS_EXIT:
SET @ErrorStatus = 0
RETURN @ErrorStatus
ERROR_EXIT:
RETURN @ErrorStatus
Translated Code¶
CREATE OR REPLACE PROCEDURE procWithLabels ()
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// SnowConvert Helpers Code section is omitted.
let ERRORSTATUS = 0;
if (ERRORSTATUS != 0) {
return ERROR_EXIT();
}
SUCCESS_EXIT();
ERROR_EXIT();
function SUCCESS_EXIT() {
ERRORSTATUS = 0;
return ERRORSTATUS;
}
function ERROR_EXIT() {
return ERRORSTATUS;
}
$$;
As you see in the example above, the return is added to the function call, in order to stop the code flow as SQL Server does with the GOTO .
Known Issues ¶
No issues were found.
Related EWIs¶
SSC-EWI-0040: Statement Not Supported.
SSC-EWI-0073: Pending Functional Equivalence Review.
Tables¶
Applies to
[x] SQL Server
[x] Azure Synapse Analytics
Note
Some parts in the output code are omitted for clarity reasons.
Basic Create Table¶
Source
CREATE TABLE [MYSCHEMA].[MYTABLE]
(
[COL1] INT IDENTITY (1,1) NOT NULL,
[COL2] INT,
[COL2 COL3 COL4] VARCHAR,
[COL VARCHAR_SPANISH] [VARCHAR](20) COLLATE Modern_Spanish_CI_AI DEFAULT 'HOLA',
[COL VARCHAR_LATIN] [VARCHAR](20) COLLATE Latin1_General_CI_AI DEFAULT 'HELLO'
);
Expected
CREATE OR REPLACE SEQUENCE MYSCHEMA.MYTABLE_COL1
START WITH 1
INCREMENT BY 1
COMMENT = 'FOR TABLE-COLUMN MYSCHEMA.MYTABLE.COL1';
CREATE OR REPLACE TABLE MYSCHEMA.MYTABLE (
COL1 INT DEFAULT MYSCHEMA.MYTABLE_COL1.NEXTVAL NOT NULL,
COL2 INT,
"COL2 COL3 COL4" VARCHAR,
"COL VARCHAR_SPANISH" VARCHAR(20) COLLATE 'ES-CI-AI' /*** SSC-PRF-0002 - CASE INSENSITIVE COLUMNS CAN DECREASE THE PERFORMANCE OF QUERIES ***/ DEFAULT 'HOLA',
"COL VARCHAR_LATIN" VARCHAR(20) COLLATE 'EN-CI-AI' /*** SSC-PRF-0002 - CASE INSENSITIVE COLUMNS CAN DECREASE THE PERFORMANCE OF QUERIES ***/ DEFAULT 'HELLO'
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
;
Temporary Tables¶
In the source code, there can be some table names that start with the character #.
CREATE TABLE #MyLocalTempTable (
COL1 INT,
COL2 INT
);
If that is the case, they are transformed into temporary tables in the output code.
Let’s see how the code from above would be migrated.
CREATE OR REPLACE TEMPORARY TABLE T_MyLocalTempTable (
COL1 INT,
COL2 INT
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;
As you can see, TEMPORARY was added to the definition of the table, and the character # was replaced with T_.
Also, all references of the table will be transformed too, to match the new name given to the temporary table.
NULL and NOT NULL Column Option¶
NULL and NOT NULL column options are supported in Snowflake.
Source
CREATE TABLE [SCHEMA1].[TABLE1](
[COL1] [varchar](20) NOT NULL
) ON [PRIMARY]
GO
CREATE TABLE [SCHEMA1].[TABLE2](
[COL1] [varchar](20) NULL
) ON [PRIMARY]
GO
Expected
CREATE OR REPLACE TABLE SCHEMA1.TABLE1 (
COL1 VARCHAR(20) NOT NULL
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;
CREATE OR REPLACE TABLE SCHEMA1.TABLE2 (
COL1 VARCHAR(20) NULL
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;
Identity Column Option¶
For identity columns, a sequence is created and assigned to the column.
Source
CREATE TABLE acct3.UnidentifiedCash3 (
UnidentifiedCash_ID3 INT IDENTITY (666, 313) NOT NULL
);
Expected
CREATE OR REPLACE SEQUENCE acct3.UnidentifiedCash3_UnidentifiedCash_ID3
START WITH 666
INCREMENT BY 313
COMMENT = 'FOR TABLE-COLUMN acct3.UnidentifiedCash3.UnidentifiedCash_ID3';
CREATE OR REPLACE TABLE acct3.UnidentifiedCash3 (
UnidentifiedCash_ID3 INT DEFAULT acct3.UnidentifiedCash3_UnidentifiedCash_ID3.NEXTVAL NOT NULL
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;
Default Column Option¶
The default Expr is supported in Snowflake, however, in Sql Server it can come together with a constraint Name. Since that part is not supported in Snowflake, it has been removed, and a warning has been added.
Source
CREATE TABLE [SCHEMA1].[TABLE1] (
[COL1] VARCHAR (10) CONSTRAINT [constraintName] DEFAULT ('0') NOT NULL
);
Expected
CREATE OR REPLACE TABLE SCHEMA1.TABLE1 (
COL1 VARCHAR(10)
--** SSC-FDM-0012 - CONSTRAINT IN DEFAULT EXPRESSION IS NOT SUPPORTED IN SNOWFLAKE **
DEFAULT ('0') NOT NULL
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;
Column Constraint¶
Source
CREATE TABLE [SalesLT].[Address](
[AddressID] [int] IDENTITY(1,1) NOT FOR REPLICATION NOT NULL,
[AddressLine1] [nvarchar](60) NOT NULL,
[AddressLine2] [nvarchar](60) NULL,
[City] [nvarchar](30) NOT NULL,
[StateProvince] [dbo].[Name] NOT NULL,
[CountryRegion] [dbo].[Name] NOT NULL,
[PostalCode] [nvarchar](15) NOT NULL,
[rowguid] [uniqueidentifier] ROWGUIDCOL NOT NULL,
[ModifiedDate] [datetime] NOT NULL,
CONSTRAINT [PK_Address_AddressID] PRIMARY KEY CLUSTERED
(
[AddressID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY],
CONSTRAINT [AK_Address_rowguid] UNIQUE NONCLUSTERED
(
[rowguid] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]
Expected
CREATE OR REPLACE SEQUENCE SalesLT.Address_AddressID
START WITH 1
INCREMENT BY 1
COMMENT = 'FOR TABLE-COLUMN SalesLT.Address.AddressID';
--** SSC-FDM-0007 - MISSING DEPENDENT OBJECT "[dbo].[Name]" **
CREATE OR REPLACE TABLE SalesLT.Address (
AddressID INT DEFAULT SalesLT.Address_AddressID.NEXTVAL NOT NULL,
AddressLine1 VARCHAR(60) NOT NULL,
AddressLine2 VARCHAR(60) NULL,
City VARCHAR(30) NOT NULL,
StateProvince VARIANT /*** SSC-FDM-TS0015 - DATA TYPE DBO.NAME IS NOT SUPPORTED IN SNOWFLAKE ***/ NOT NULL,
CountryRegion VARIANT /*** SSC-FDM-TS0015 - DATA TYPE DBO.NAME IS NOT SUPPORTED IN SNOWFLAKE ***/ NOT NULL,
PostalCode VARCHAR(15) NOT NULL,
rowguid VARCHAR
!!!RESOLVE EWI!!! /*** SSC-EWI-0040 - THE STATEMENT IS NOT SUPPORTED IN SNOWFLAKE ***/!!!
ROWGUIDCOL NOT NULL,
ModifiedDate TIMESTAMP_NTZ(3) NOT NULL,
CONSTRAINT PK_Address_AddressID PRIMARY KEY (AddressID),
CONSTRAINT AK_Address_rowguid UNIQUE (rowguid)
)
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": { "major": 0, "minor": 0, "patch": "0" }, "attributes": { "component": "transact", "convertedOn": "09/23/2024" }}'
;
Collate Column Option¶
For the Collate transformation, please check the following link.
ENCRYPTED WITH Column Option¶
The Encrypted With is not supported in Snowflake, so it is being removed, and a warning is added.
Source
CREATE TABLE [SCHEMA1].[TABLE1] (
[COL1] NVARCHAR(60) ENCRYPTED WITH (COLUMN_ENCRYPTION_KEY = MyCEK, ENCRYPTION_TYPE = RANDOMIZED, ALGORITHM = 'AEAD_AES_256_CBC_HMAC_SHA_256')
);
Expected
CREATE OR REPLACE TABLE SCHEMA1.TABLE1 (
COL1 VARCHAR(60)
-- --** SSC-FDM-TS0009 - ENCRYPTED WITH NOT SUPPORTED IN SNOWFLAKE **
-- ENCRYPTED WITH (COLUMN_ENCRYPTION_KEY = MyCEK, ENCRYPTION_TYPE = RANDOMIZED, ALGORITHM = 'AEAD_AES_256_CBC_HMAC_SHA_256')
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;
NOT FOR REPLICATION¶
The NOT FOR REPLICATION option is not supported in Snowflake. It is used for the identity that is being migrated to a SEQUENCE.
Warning
Notice that NOT FOR REPLICATION is a statement that is not required in Snowflake because it is translated to an equivalent, so it is removed.
Source
CREATE TABLE [TABLE1] (
[COL1] INT IDENTITY (1, 1) NOT FOR REPLICATION NOT NULL
) ON [PRIMARY];
Output
CREATE OR REPLACE SEQUENCE TABLE1_COL1
START WITH 1
INCREMENT BY 1
COMMENT = 'FOR TABLE-COLUMN TABLE1.COL1';
CREATE OR REPLACE TABLE TABLE1 (
COL1 INT DEFAULT TABLE1_COL1.NEXTVAL NOT NULL
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;
On Primary¶
The ON PRIMARY option is a statement that is used in SQL Server to define on which file an object, e.g. a table, is going to be created. Such as on a primary or secondary file group inside the database. Snowflake provides a different logic and indicates distinct constraints. Please review the following Snowflake documentation for more information.
Source¶
CREATE TABLE [TABLE1](
[COL1] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL
CONSTRAINT [pk_dimAddress_AddressId] PRIMARY KEY CLUSTERED ([COL1])
WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]
Output¶
CREATE OR REPLACE TABLE TABLE1 (
COL1 VARCHAR(255) COLLATE 'EN-CI-AS' /*** SSC-PRF-0002 - CASE INSENSITIVE COLUMNS CAN DECREASE THE PERFORMANCE OF QUERIES ***/ /*** SSC-FDM-TS0002 - COLLATION FOR VALUE CP1 NOT SUPPORTED ***/ NOT NULL
CONSTRAINT pk_dimAddress_AddressId PRIMARY KEY (COL1)
)
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": { "major": 0, "minor": 0, "patch": "0" }, "attributes": { "component": "transact", "convertedOn": "09/23/2024" }}'
;
ASC/DESC Column Sorting¶
Column sorting is not supported in Snowflake, the ASC or DESC keywords are being removed.
Source¶
CREATE TABLE [TABLE1](
[COL1] [int] NOT NULL,
CONSTRAINT [constraint1] PRIMARY KEY CLUSTERED ([COL1] ASC)
) ON [PRIMARY]
Output¶
CREATE OR REPLACE TABLE TABLE1 (
COL1 INT NOT NULL,
CONSTRAINT constraint1 PRIMARY KEY (COL1)
)
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": { "major": 0, "minor": 0, "patch": "0" }, "attributes": { "component": "transact", "convertedOn": "09/23/2024" }}'
;
Computed Columns¶
Computed columns are supported in Snowflake, we just need to add the explicit data type in order to be able to deploy the table, for example.
Source¶
CREATE TABLE [TABLE1](
[COL2] [int] NOT NULL,
[COL2] [int] NOT NULL,
[COL1] AS (COL3 * COL2),
)
Output¶
CREATE OR REPLACE TABLE TABLE1 (
COL2 INT NOT NULL,
COL2 INT NOT NULL,
COL1 VARIANT AS (COL3 * COL2) /*** SSC-FDM-TS0014 - COMPUTED COLUMN WAS TRANSFORMED TO ITS SNOWFLAKE EQUIVALENT, FUNCTIONAL EQUIVALENCE VERIFICATION PENDING. ***/
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;
If the computed expression cannot transform, a warning is added, and a simple column definition with the expression return type will be used instead, like in the following example:
Source¶
CREATE TABLE [TABLE1](
[Col1] AS (CONVERT ([XML], ExpressionValue))
)
The expression CONVERT ([NUMERIC], ExpressionValue) is not supported yet by SnowConvert, so, after it is inspected, SnowConvert will determine that its type is XML, so the transformation will be
CREATE OR REPLACE TABLE TABLE1 (
Col1 TEXT AS (CAST(ExpressionValue AS VARIANT !!!RESOLVE EWI!!! /*** SSC-EWI-0036 - XML DATA TYPE CONVERTED TO VARIANT ***/!!!)) /*** SSC-FDM-TS0014 - COMPUTED COLUMN WAS TRANSFORMED TO ITS SNOWFLAKE EQUIVALENT, FUNCTIONAL EQUIVALENCE VERIFICATION PENDING. ***/
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;
SnowConvert will run a process to determine the original expression type in SQL Server. However, the column will have the equivalent target type. In the previous example, the column type in SQLServer was XML, but the target type in Snowflake for storing an XML is TEXT. For more information about data type mapping, check the data types sections.
MASKED WITH Column Option¶
In SQL Server the data masking is used to keep sensitive information from nonprivileged users. Review the SQL SERVER documentation for more information. In Snowflake, there is a dynamic data masking functionality but it is available to Enterprise Edition only. Please review the following Snowflake documentation.
Input¶
CREATE TABLE TABLE1
(
[COL1] [nvarchar](50) MASKED WITH (FUNCTION = 'default()') NULL
);
Output¶
CREATE OR REPLACE TABLE TABLE1
(
COL1 VARCHAR(50)
!!!RESOLVE EWI!!! /*** SSC-EWI-TS0017 - COLUMN MASKING NOT SUPPORTED IN CREATE TABLE ***/!!!
MASKED WITH (FUNCTION = 'default()') NULL
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;
ROWGUIDCOL Column Option¶
ROWGUIDCOL is no longer applicable in Snowflake. It is used in SQL Server for UNIQUEIDENTIFIER types that are currently translated to VARCHAR. For example:
Input¶
CREATE TABLE TABLEROWID (
[ROWGUID] UNIQUEIDENTIFIER ROWGUIDCOL NOT NULL
) ON [PRIMARY];
Output¶
CREATE OR REPLACE TABLE TABLEROWID (
ROWGUID VARCHAR
!!!RESOLVE EWI!!! /*** SSC-EWI-0040 - THE STATEMENT IS NOT SUPPORTED IN SNOWFLAKE ***/!!!
ROWGUIDCOL NOT NULL
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;
GENERATED ALWAYS AS ROW START/END Column Option¶
ROW START/END is not supported in Snowflake. An error is added when SnowConvert try to transform this kind of column option.
Input¶
CREATE TABLE TABLEROWID (
[COL1] DATETIME GENERATED ALWAYS AS ROW START NOT NULL
) ON [PRIMARY];
Output¶
CREATE OR REPLACE TABLE TABLEROWID (
COL1 TIMESTAMP_NTZ(3) GENERATED ALWAYS AS ROW START !!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'GeneratedClause' NODE ***/!!! NOT NULL
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;
Known Issues¶
No issues were found.
Related EWIs¶
SSC-EWI-0036: Data type converted to another data type.
SSC-EWI-0040: Statement Not Supported.
SSC-EWI-0073: Pending Functional Equivalence Review.
SSC-EWI-TS0017: Masking not supported.
SSC-FDM-0012: Constraint in default expression is not supported.
SSC-FDM-TS0002: This message is shown when there is a collate clause that is not supported in Snowflake.
SSC-FDM-TS0009: Encrypted with not supported in Snowflake.
SSC-FDM-TS0014: Computed column transformed.
SSC-FDM-TS0015: Data type is not supported in Snowflake.
SSC-PRF-0002: Case-insensitive columns can decrease the performance of queries.
Views¶
Applies to
[x] SQL Server
[x] Azure Synapse Analytics
Note
Some parts in the output code are omitted for clarity reasons.
In this section, we will check the transformation for the create view.
Sample Source Patterns¶
SIMPLE CREATE VIEW¶
The following example shows a transformation for a simple CREATE VIEW statement.
CREATE VIEW VIEWNAME
AS
SELECT AValue from ATable;
Expected
CREATE OR REPLACE VIEW VIEWNAME
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
AS
SELECT
AValue
from
ATable;
CREATE OR ALTER VIEW¶
The CREATE OR ALTER definition used in SqlServer is transformed to CREATE OR REPLACE in Snowflake.
CREATE OR ALTER VIEW VIEWNAME
AS
SELECT AValue from ATable;
CREATE OR REPLACE VIEW VIEWNAME
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
AS
SELECT
AValue
from
ATable;
CREATE VIEW WITH¶
In this type of View, after the name of the View, the following clauses can come
WITH ENCRYPTIONWITH SCHEMABINDINGWITH VIEW_METADATA
Warning
Notice that the above clauses are removed from the translation. because are not relevant in Snowflake syntax.
CREATE OR ALTER VIEW VIEWNAME
WITH ENCRYPTION
AS
SELECT AValue from ATable;
CREATE OR REPLACE VIEW VIEWNAME
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
AS
SELECT
AValue
from
ATable;
CREATE VIEW AS SELECT WITH CHECK OPTION¶
In this type of View, the clause WITH CHECK OPTION comes after the end of the Select statement used in the Create View.
Warning
Notice that WITH CHECK OPTIONis removed from the translation, because is not relevant in Snowflake syntax.
CREATE OR ALTER VIEW VIEWNAME
AS
SELECT AValue from ATable
WITH CHECK OPTION;
Expected
CREATE OR REPLACE VIEW VIEWNAME
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
AS
SELECT
AValue
from
ATable;
CREATE VIEW AS COMMON TABLE EXPRESSION¶
Common Table Expressions must be used to retrieve the data:
CREATE VIEW EMPLOYEEIDVIEW
AS
WITH CTE AS ( SELECT NationalIDNumber from [HumanResources].[Employee]
UNION ALL
SELECT BusinessEntityID FROM [HumanResources].[EmployeeDepartmentHistory] )
SELECT * FROM MyCTE;
CREATE OR REPLACE VIEW EMPLOYEEIDVIEW
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
AS
--** SSC-PRF-TS0001 - PERFORMANCE WARNING - RECURSION FOR CTE NOT CHECKED. MIGHT REQUIRE RECURSIVE KEYWORD **
WITH CTE AS ( SELECT
NationalIDNumber
from
HumanResources.Employee
UNION ALL
SELECT
BusinessEntityID
FROM
HumanResources.EmployeeDepartmentHistory
)
SELECT
*
FROM
MyCTE;
UNSUPPORTED SCENARIOS¶
Common table expressions with Update, Insert or Delete statements will be commented out because they are not supported in Snowflake and SQLServer.
In the case where an invalid CTE is added to the view, this will be completely commented out.
--!!!RESOLVE EWI!!! /*** SSC-EWI-0021 - COMMON TABLE EXPRESSION IN VIEW NOT SUPPORTED ***/!!!
--CREATE OR REPLACE VIEW PUBLIC.EmployeeInsertVew
--AS
--WITH MyCTE AS ( SELECT
--NationalIDNumber
--from
--HumanResources.Employee
--UNION ALL
--SELECT
--BusinessEntityID
--FROM
--HumanResources.EmployeeDepartmentHistory
--)
--INSERT INTO PUBLIC.Dummy
FINAL SAMPLE¶
Let’s see a final sample, let’s put together all the cases that we have seen so far and see how the transformation would be
CREATE OR ALTER VIEW VIEWNAME
WITH ENCRYPTION
AS
Select AValue from ATable
WITH CHECK OPTION;
Expected
CREATE OR REPLACE VIEW VIEWNAME
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
AS
Select
AValue
from
ATable;
As you can see, we changed the OR ALTER with OR REPLACE and we removed the clause WITH ENCRYPTION that comes after the view name and the WITH CHECK OPTION that comes after the Select.
Related EWIs¶
SSC-PRF-TS0001: Performance warning - recursion for CTE not checked. Might require a recursive keyword.
Azure Synapse Analytics¶
Applies to
[x] Azure Synapse Analytics
Description¶
This section presents the translation for syntax specific to Azure Synapse Analytics Tables.
Note
For most patterns, check the translation specification for general tables, as they share almost the same syntax and behavior.
Create Table¶
CREATE TABLE { database_name.schema_name.table_name | schema_name.table_name | table_name }
(
{ column_name <data_type> [ <column_options> ] } [ ,...n ]
)
[ WITH ( <table_option> [ ,...n ] ) ]
[;]
Create Table As¶
CREATE TABLE { database_name.schema_name.table_name | schema_name.table_name | table_name }
[ ( column_name [ ,...n ] ) ]
WITH (
<distribution_option> -- required
[ , <table_option> [ ,...n ] ]
)
AS <select_statement>
OPTION <query_hint>
[;]
Sample Source Patterns¶
WITH table options¶
Azure Synapse Analytics presents an additional syntax for defining table options.
<table_option> ::=
{
CLUSTERED COLUMNSTORE INDEX -- default for Azure Synapse Analytics
| CLUSTERED COLUMNSTORE INDEX ORDER (column [,...n])
| HEAP --default for Parallel Data Warehouse
| CLUSTERED INDEX ( { index_column_name [ ASC | DESC ] } [ ,...n ] ) -- default is ASC
}
{
DISTRIBUTION = HASH ( distribution_column_name )
| DISTRIBUTION = HASH ( [distribution_column_name [, ...n]] )
| DISTRIBUTION = ROUND_ROBIN -- default for Azure Synapse Analytics
| DISTRIBUTION = REPLICATE -- default for Parallel Data Warehouse
}
| PARTITION ( partition_column_name RANGE [ LEFT | RIGHT ] -- default is LEFT
FOR VALUES ( [ boundary_value [,...n] ] ) )
Snowflake automatically handles table optimization through mechanisms like micro-partitioning. For this reason, an equivalent syntax for some of these table options does not exist in Snowflake. Therefore, it is not necessary to define some of Transact’s table options.
Table options that will be omitted:
CLUSTERED COLUMNSTORE INDEX (without column)
HEAP
DISTRIBUTION
PARTITION
CLUSTERED [ COLUMNSTORE ] INDEX with columns, will be transformed to Snowflake’s CLUSTER BY. A performance review PRF will be added as it is advised to check if defining a CLUSTER KEY is necessary.
Transact¶
CREATE TABLE my_table (
enterprise_cif INT,
name NVARCHAR(100),
address NVARCHAR(255),
created_at DATETIME
)
WITH (
DISTRIBUTION = HASH(enterprise_cif),
CLUSTERED INDEX (enterprise_cif)
);
Snowflake¶
CREATE OR REPLACE TABLE my_table (
enterprise_cif INT,
name VARCHAR(100),
address VARCHAR(255),
created_at TIMESTAMP_NTZ(3)
)
--** SSC-PRF-0007 - PERFORMANCE REVIEW - CLUSTER BY **
CLUSTER BY (enterprise_cif)
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": { "major": 0, "minor": 0, "patch": "0" }, "attributes": { "component": "transact", "convertedOn": "10/09/2024" }}'
;
Known Issues¶
No issues were found.
Related EWIs¶
SSC-PRF-0007: PERFORMANCE REVIEW - CLUSTER BY.
TEXTIMAGE_ON¶
Applies to
[x] SQL Server
Note
Non-relevant statement.
Warning
Notice that this statement isremoved from the migrationbecause it is a non-relevant syntax. It means that it is not required in Snowflake.
Description¶
TEXTIMAGE_ON [PRIMARY] is a way in Transact to handle the large information groups inside a table. In Snowflake it is not required to define these kinds of characteristics because Snowflake handles large data files or information in a different arrangement.
Sample Source Patterns¶
Notice that in this example the TEXTIMAGE_ON [PRIMARY] has been removed due to the unnecessary syntax.
CREATE TABLE [dbo].[TEST_Person](
[date_updated] [datetime] NULL
) TEXTIMAGE_ON [PRIMARY]
CREATE OR REPLACE TABLE dbo.TEST_Person (
date_updated TIMESTAMP_NTZ(3) NULL
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
;
Known Issues ¶
No issues were found.
Related EWIs ¶
No related EWIs.
FUNCTION¶
Applies to
[x] SQL Server
[x] Azure Synapse Analytics
Description¶
SQL Server only supports two types of User Defined Functions:
Using these UDFs types, is possible to subcategorized them into simple and complex, according to the inner logic.
Simple UDFs, matches the SQL Server syntax with Snowflake syntax. This type doesn’t add any logic and goes straightforward to the result. These are usually match to Snowflake’s SQL UDFs.
Complex UDFs, makes extensive use of a particular statements (INSERT, DELETE, UPDATE, SET, DECLARE, etc) or control-of-flow blocks (IF…ELSE, WHILE, etc) and usually represents a mismatch or violation to Snowflake’s SQL UDFs definition.
Limitations¶
Transact UDFs have some limitations not present in other database engines (such as Oracle and Teradata). These limitations helps the translations by narrowing the failure scope. This means, there are specific scenarios we can expect to avoid.
Here are some of the limitations SQL Server has on UDFs
UDFs cannot be used to perform actions that modify the database state
User-defined functions cannot contain an OUTPUT INTO clause that has a table as its target
User-defined functions cannot return multiple result sets. Use a stored procedure if you need to return multiple result sets.
For the full list, please check this link Create User-defined Functions (Database engine)
INLINE TABLE-VALUED¶
Applies to
[x] SQL Server
[x] Azure Synapse Analytics
Description¶
Note
Some parts in the output code are omitted for clarity reasons.
Inline Table-Valued functions are table expression that can accept parameters, perform a SELECT statement and return a TABLE (SQL Server Language Reference Creating an inline table-valued function).
Transact Syntax¶
-- Transact-SQL Inline Table-Valued Function Syntax
CREATE [ OR ALTER ] FUNCTION [ schema_name. ] function_name
( [ { @parameter_name [ AS ] [ type_schema_name. ] parameter_data_type
[ = default ] [ READONLY ] }
[ ,...n ]
]
)
RETURNS TABLE
[ WITH <function_option> [ ,...n ] ]
[ AS ]
RETURN [ ( ] select_stmt [ ) ]
[ ; ]
Snowflake SQL Syntax¶
CREATE OR REPLACE FUNCTION <name> ( [ <arguments> ] )
RETURNS TABLE ( <output_col_name> <output_col_type> [, <output_col_name> <output_col_type> ... ] )
AS '<sql_expression>'sql
Sample Source Patterns¶
The following section describes all the possible source code patterns that can appear in this kind of CREATE FUNCTION syntax.
For Inline Table-Valued functions, there can only exist one statement per body that could be:
SELECTStatementWITHCommon Table Expression
Select and return values directly from one table¶
This is the simplest scenario, performing a simple select from a table and returning those values
Transact-SQL¶
CREATE FUNCTION GetDepartmentInfo()
RETURNS TABLE
AS
RETURN
(
SELECT DepartmentID, Name, GroupName
FROM HumanResources.Department
);
GO
SELECT * from GetDepartmentInfo()
DepartmentID|Name |GroupName |
------------+--------------------------+------------------------------------+
1|Engineering |Research and Development |
2|Tool Design |Research and Development |
3|Sales |Sales and Marketing |
4|Marketing |Sales and Marketing |
5|Purchasing |Inventory Management |
6|Research and Development |Research and Development |
7|Production |Manufacturing |
8|Production Control |Manufacturing |
9|Human Resources |Executive General and Administration|
10|Finance |Executive General and Administration|
11|Information Services |Executive General and Administration|
12|Document Control |Quality Assurance |
13|Quality Assurance |Quality Assurance |
14|Facilities and Maintenance|Executive General and Administration|
15|Shipping and Receiving |Inventory Management |
16|Executive |Executive General and Administration|
Snowflake SQL¶
CREATE OR REPLACE FUNCTION GetDepartmentInfo ()
RETURNS TABLE(
DepartmentID STRING /*** SSC-FDM-TS0012 - INFORMATION FOR THE COLUMN DepartmentID WAS NOT FOUND. STRING DATATYPE USED TO MATCH CAST AS STRING OPERATION ***/,
Name STRING /*** SSC-FDM-TS0012 - INFORMATION FOR THE COLUMN Name WAS NOT FOUND. STRING DATATYPE USED TO MATCH CAST AS STRING OPERATION ***/,
GroupName STRING /*** SSC-FDM-TS0012 - INFORMATION FOR THE COLUMN GroupName WAS NOT FOUND. STRING DATATYPE USED TO MATCH CAST AS STRING OPERATION ***/
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
AS
$$
SELECT
CAST(DepartmentID AS STRING),
CAST(Name AS STRING),
CAST(GroupName AS STRING)
FROM
HumanResources.Department
$$;
SELECT
*
from
TABLE(GetDepartmentInfo());
DepartmentID|Name |GroupName |
------------+--------------------------+------------------------------------+
1|Engineering |Research and Development |
2|Tool Design |Research and Development |
3|Sales |Sales and Marketing |
4|Marketing |Sales and Marketing |
5|Purchasing |Inventory Management |
6|Research and Development |Research and Development |
7|Production |Manufacturing |
8|Production Control |Manufacturing |
9|Human Resources |Executive General and Administration|
10|Finance |Executive General and Administration|
11|Information Services |Executive General and Administration|
12|Document Control |Quality Assurance |
13|Quality Assurance |Quality Assurance |
14|Facilities and Maintenance|Executive General and Administration|
15|Shipping and Receiving |Inventory Management |
16|Executive |Executive General and Administration|
Select and return values from multiple tables renaming columns and using built in functions¶
This is an example of a query using built-in functions in a select statement getting data from different tables, renaming columns and returning a table.
Transact-SQL¶
CREATE FUNCTION GetPersonBasicInfo()
RETURNS TABLE
AS
RETURN
(
SELECT TOP (20)
P.PersonType,
P.FirstName,
E.JobTitle,
E.Gender,
YEAR(E.HireDate) as HIREYEAR
FROM
Person.Person P
INNER JOIN
HumanResources.Employee E
ON
P.BusinessEntityID = E.BusinessEntityID
);
GO
SELECT * FROM GetPersonBasicInfo();
PersonType|FirstName|JobTitle |Gender|HIREYEAR|
----------+---------+---------------------------------+------+--------+
EM |Ken |Chief Executive Officer |M | 2009|
EM |Terri |Vice President of Engineering |F | 2008|
EM |Roberto |Engineering Manager |M | 2007|
EM |Rob |Senior Tool Designer |M | 2007|
EM |Gail |Design Engineer |F | 2008|
EM |Jossef |Design Engineer |M | 2008|
EM |Dylan |Research and Development Manager |M | 2009|
EM |Diane |Research and Development Engineer|F | 2008|
EM |Gigi |Research and Development Engineer|F | 2009|
EM |Michael |Research and Development Manager |M | 2009|
EM |Ovidiu |Senior Tool Designer |M | 2010|
EM |Thierry |Tool Designer |M | 2007|
EM |Janice |Tool Designer |F | 2010|
EM |Michael |Senior Design Engineer |M | 2010|
EM |Sharon |Design Engineer |F | 2011|
EM |David |Marketing Manager |M | 2007|
EM |Kevin |Marketing Assistant |M | 2007|
EM |John |Marketing Specialist |M | 2011|
EM |Mary |Marketing Assistant |F | 2011|
EM |Wanida |Marketing Assistant |F | 2011|
Snowflake SQL¶
CREATE OR REPLACE FUNCTION GetPersonBasicInfo ()
RETURNS TABLE(
PersonType STRING /*** SSC-FDM-TS0012 - INFORMATION FOR THE COLUMN PersonType WAS NOT FOUND. STRING DATATYPE USED TO MATCH CAST AS STRING OPERATION ***/,
FirstName STRING /*** SSC-FDM-TS0012 - INFORMATION FOR THE COLUMN FirstName WAS NOT FOUND. STRING DATATYPE USED TO MATCH CAST AS STRING OPERATION ***/,
JobTitle STRING /*** SSC-FDM-TS0012 - INFORMATION FOR THE COLUMN JobTitle WAS NOT FOUND. STRING DATATYPE USED TO MATCH CAST AS STRING OPERATION ***/,
Gender STRING /*** SSC-FDM-TS0012 - INFORMATION FOR THE COLUMN Gender WAS NOT FOUND. STRING DATATYPE USED TO MATCH CAST AS STRING OPERATION ***/,
HIREYEAR INTEGER
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
AS
$$
SELECT
TOP 20
CAST(P.PersonType AS STRING),
CAST(P.FirstName AS STRING),
CAST(E.JobTitle AS STRING),
CAST(E.Gender AS STRING),
YEAR(E.HireDate :: TIMESTAMP) as HIREYEAR
FROM
Person.Person P
INNER JOIN
HumanResources.Employee E
ON P.BusinessEntityID = E.BusinessEntityID
$$;
SELECT
*
FROM
TABLE(GetPersonBasicInfo());
PersonType|FirstName|JobTitle |Gender|HIREYEAR|
----------+---------+---------------------------------+------+--------+
EM |Ken |Chief Executive Officer |M | 2009|
EM |Terri |Vice President of Engineering |F | 2008|
EM |Roberto |Engineering Manager |M | 2007|
EM |Rob |Senior Tool Designer |M | 2007|
EM |Gail |Design Engineer |F | 2008|
EM |Jossef |Design Engineer |M | 2008|
EM |Dylan |Research and Development Manager |M | 2009|
EM |Diane |Research and Development Engineer|F | 2008|
EM |Gigi |Research and Development Engineer|F | 2009|
EM |Michael |Research and Development Manager |M | 2009|
EM |Ovidiu |Senior Tool Designer |M | 2010|
EM |Thierry |Tool Designer |M | 2007|
EM |Janice |Tool Designer |F | 2010|
EM |Michael |Senior Design Engineer |M | 2010|
EM |Sharon |Design Engineer |F | 2011|
EM |David |Marketing Manager |M | 2007|
EM |Kevin |Marketing Assistant |M | 2007|
EM |John |Marketing Specialist |M | 2011|
EM |Mary |Marketing Assistant |F | 2011|
EM |Wanida |Marketing Assistant |F | 2011|
Select columns using WITH statement¶
The body of an inline table-valued function can also be specified using a WITH statement as shown below.
Transact-SQL¶
CREATE FUNCTION GetMaritalStatusByGender
(
@P_Gender nchar(1)
)
RETURNS TABLE
AS
RETURN
(
WITH CTE AS
(
SELECT BusinessEntityID, MaritalStatus, Gender
FROM HumanResources.Employee
where Gender = @P_Gender
)
SELECT
MaritalStatus, Gender, CONCAT(P.FirstName,' ', P.LastName) as Name
FROM
CTE INNER JOIN Person.Person P
ON
CTE.BusinessEntityID = P.BusinessEntityID
);
GO
select * from GetMaritalStatusByGender('F');
MaritalStatus|Gender|Name |
-------------+------+-----------------------+
S |F |Terri Duffy |
M |F |Gail Erickson |
S |F |Diane Margheim |
M |F |Gigi Matthew |
M |F |Janice Galvin |
M |F |Sharon Salavaria |
S |F |Mary Dempsey |
M |F |Wanida Benshoof |
M |F |Mary Gibson |
M |F |Jill Williams |
S |F |Jo Brown |
M |F |Britta Simon |
M |F |Margie Shoop |
M |F |Rebecca Laszlo |
M |F |Suchitra Mohan |
M |F |Kim Abercrombie |
S |F |JoLynn Dobney |
M |F |Nancy Anderson |
M |F |Ruth Ellerbrock |
M |F |Doris Hartwig |
M |F |Diane Glimp |
M |F |Bonnie Kearney |
M |F |Denise Smith |
S |F |Diane Tibbott |
M |F |Carole Poland |
M |F |Carol Philips |
M |F |Merav Netz |
S |F |Betsy Stadick |
S |F |Danielle Tiedt |
S |F |Kimberly Zimmerman |
M |F |Elizabeth Keyser |
M |F |Mary Baker |
M |F |Alice Ciccu |
M |F |Linda Moschell |
S |F |Angela Barbariol |
S |F |Kitti Lertpiriyasuwat |
S |F |Susan Eaton |
S |F |Kim Ralls |
M |F |Nicole Holliday |
S |F |Anibal Sousa |
M |F |Samantha Smith |
S |F |Olinda Turner |
S |F |Cynthia Randall |
M |F |Sandra Reátegui Alayo |
S |F |Linda Randall |
S |F |Shelley Dyck |
S |F |Laura Steele |
S |F |Susan Metters |
S |F |Katie McAskill-White |
M |F |Barbara Decker |
M |F |Yvonne McKay |
S |F |Janeth Esteves |
M |F |Brenda Diaz |
M |F |Lorraine Nay |
M |F |Paula Nartker |
S |F |Lori Kane |
M |F |Kathie Flood |
S |F |Belinda Newman |
M |F |Karen Berge |
M |F |Lori Penor |
M |F |Jo Berry |
M |F |Laura Norman |
M |F |Paula Barreto de Mattos|
M |F |Mindy Martin |
M |F |Deborah Poe |
S |F |Candy Spoon |
M |F |Barbara Moreland |
M |F |Janet Sheperdigian |
S |F |Wendy Kahn |
S |F |Sheela Word |
M |F |Linda Meisner |
S |F |Erin Hagens |
M |F |Annette Hill |
S |F |Jean Trenary |
S |F |Stephanie Conroy |
S |F |Karen Berg |
M |F |Janaina Bueno |
M |F |Linda Mitchell |
S |F |Jillian Carson |
S |F |Pamela Ansman-Wolfe |
S |F |Lynn Tsoflias |
M |F |Amy Alberts |
S |F |Rachel Valdez |
M |F |Jae Pak |
Snowflake SQL¶
CREATE OR REPLACE FUNCTION GetMaritalStatusByGender
(P_GENDER STRING
)
RETURNS TABLE(
MaritalStatus STRING /*** SSC-FDM-TS0012 - INFORMATION FOR THE COLUMN MaritalStatus WAS NOT FOUND. STRING DATATYPE USED TO MATCH CAST AS STRING OPERATION ***/,
Gender STRING /*** SSC-FDM-TS0012 - INFORMATION FOR THE COLUMN Gender WAS NOT FOUND. STRING DATATYPE USED TO MATCH CAST AS STRING OPERATION ***/,
Name VARCHAR
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
AS
$$
--** SSC-PRF-TS0001 - PERFORMANCE WARNING - RECURSION FOR CTE NOT CHECKED. MIGHT REQUIRE RECURSIVE KEYWORD **
WITH CTE AS
(
SELECT
BusinessEntityID,
MaritalStatus,
Gender
FROM
HumanResources.Employee
where
Gender = :P_GENDER
)
SELECT
CAST(MaritalStatus AS STRING),
CAST(Gender AS STRING),
CONCAT(P.FirstName,' ', P.LastName) as Name
FROM
CTE
INNER JOIN
Person.Person P
ON CTE.BusinessEntityID = P.BusinessEntityID
$$;
select
*
from GetMaritalStatusByGender('F') !!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'TableValuedFunctionCall' NODE ***/!!!;
MaritalStatus|Gender|Name |
-------------+------+-----------------------+
S |F |Terri Duffy |
M |F |Gail Erickson |
S |F |Diane Margheim |
M |F |Gigi Matthew |
M |F |Janice Galvin |
M |F |Sharon Salavaria |
S |F |Mary Dempsey |
M |F |Wanida Benshoof |
M |F |Mary Gibson |
M |F |Jill Williams |
S |F |Jo Brown |
M |F |Britta Simon |
M |F |Margie Shoop |
M |F |Rebecca Laszlo |
M |F |Suchitra Mohan |
M |F |Kim Abercrombie |
S |F |JoLynn Dobney |
M |F |Nancy Anderson |
M |F |Ruth Ellerbrock |
M |F |Doris Hartwig |
M |F |Diane Glimp |
M |F |Bonnie Kearney |
M |F |Denise Smith |
S |F |Diane Tibbott |
M |F |Carole Poland |
M |F |Carol Philips |
M |F |Merav Netz |
S |F |Betsy Stadick |
S |F |Danielle Tiedt |
S |F |Kimberly Zimmerman |
M |F |Elizabeth Keyser |
M |F |Mary Baker |
M |F |Alice Ciccu |
M |F |Linda Moschell |
S |F |Angela Barbariol |
S |F |Kitti Lertpiriyasuwat |
S |F |Susan Eaton |
S |F |Kim Ralls |
M |F |Nicole Holliday |
S |F |Anibal Sousa |
M |F |Samantha Smith |
S |F |Olinda Turner |
S |F |Cynthia Randall |
M |F |Sandra Reátegui Alayo |
S |F |Linda Randall |
S |F |Shelley Dyck |
S |F |Laura Steele |
S |F |Susan Metters |
S |F |Katie McAskill-White |
M |F |Barbara Decker |
M |F |Yvonne McKay |
S |F |Janeth Esteves |
M |F |Brenda Diaz |
M |F |Lorraine Nay |
M |F |Paula Nartker |
S |F |Lori Kane |
M |F |Kathie Flood |
S |F |Belinda Newman |
M |F |Karen Berge |
M |F |Lori Penor |
M |F |Jo Berry |
M |F |Laura Norman |
M |F |Paula Barreto de Mattos|
M |F |Mindy Martin |
M |F |Deborah Poe |
S |F |Candy Spoon |
M |F |Barbara Moreland |
M |F |Janet Sheperdigian |
S |F |Wendy Kahn |
S |F |Sheela Word |
M |F |Linda Meisner |
S |F |Erin Hagens |
M |F |Annette Hill |
S |F |Jean Trenary |
S |F |Stephanie Conroy |
S |F |Karen Berg |
M |F |Janaina Bueno |
M |F |Linda Mitchell |
S |F |Jillian Carson |
S |F |Pamela Ansman-Wolfe |
S |F |Lynn Tsoflias |
M |F |Amy Alberts |
S |F |Rachel Valdez |
M |F |Jae Pak |
Known issues¶
No issues were found
Related EWIs¶
SSC-FDM-TS0012: Information for the expression was not found. CAST to STRING used
SSC-PRF-TS0001: Performance warning - recursion for CTE not checked. Might require a recursive keyword.
SSC-EWI-0073: Pending Functional Equivalence Review
MULTI-STATEMENT TABLE-VALUED¶
Applies to
[x] SQL Server
[x] Azure Synapse Analytics
Note
Some parts in the output code are omitted for clarity reasons.
Note
All the code samples on this page have not been implemented yet in SnowConvert. They should be interpreted as a reference for how each scenario should be translated to Snowflake. These translations may change in the future.Some parts in the output code are omitted for clarity reasons.
Description¶
Multi-statement table-valued is similar to Inline-statement table-valued (INLINE TABLE-VALUED. However Multi-statement table-valued may have more than one statement in its function body, the table columns are specified in the return type and it has a BEGIN/END block (SQL Server Language Reference Creating a multi-statement table-valued function
Transact-SQL Syntax¶
CREATE [ OR ALTER ] FUNCTION [ schema_name. ] function_name
( [ { @parameter_name [ AS ] [ type_schema_name. ] parameter_data_type
[ = default ] [READONLY] }
[ ,...n ]
]
)
RETURNS @return_variable TABLE <table_type_definition>
[ WITH <function_option> [ ,...n ] ]
[ AS ]
BEGIN
function_body
RETURN
END
[ ; ]
Snowflake SQL¶
CREATE OR REPLACE FUNCTION <name> ( [ <arguments> ] )
RETURNS TABLE ( <output_col_name> <output_col_type> [, <output_col_name> <output_col_type> ... ] )
AS '<sql_expression>'
Sample Source Patterns¶
The following section describes all the possible source code patterns that can appear in this kind of CREATE FUNCTION syntax.
The function body of Multi-Statement Table-Valued function must be a SELECT statement. For this reason the others statements must be called separately.
Insert values in a table¶
Inserts one or more rows into the table and returns the table with the new values
Transact-SQL¶
CREATE OR ALTER FUNCTION calc_behavioral_segment()
RETURNS @behavioral_segments TABLE (behavioral_segment VARCHAR(50))
AS
BEGIN
DECLARE @col varchar(15)
SET @col = 'Unknown'
INSERT INTO @behavioral_segments
SELECT @col
RETURN
END
SELECT * FROM calc_behavioral_segment();
BEHAVIORAL_SEGMENT|
------------------+
Unknown|
Snowflake SQL¶
!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'TABLE VALUED FUNCTIONS' NODE ***/!!!
CREATE OR ALTER FUNCTION calc_behavioral_segment ()
RETURNS BEHAVIORAL_SEGMENTS TABLE (
behavioral_segment VARCHAR(50))
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
BEGIN
DECLARE @col varchar(15)
SET @col = 'Unknown'
INSERT INTO @behavioral_segments
SELECT @col
RETURN
END
SELECT * FROM calc_behavioral_segment();;
BEHAVIORAL_SEGMENT|
------------------+
Unknown|
Insert value according to if/else statement¶
Inserts a row into the table according to the condition and returns the table with the new value
Transact-SQL¶
CREATE OR ALTER FUNCTION odd_or_even_number(@number INT)
RETURNS @numbers TABLE (number_type VARCHAR(15))
AS
BEGIN
IF ((@number % 2) = 0)
BEGIN
INSERT @numbers SELECT 'Even'
END
ELSE
BEGIN
INSERT @numbers SELECT 'Odd'
END
RETURN
END
SELECT * FROM odd_or_even_number(9);
NUMBER_TYPE|
------------------+
Odd|
Snowflake SQL¶
!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'TABLE VALUED FUNCTIONS' NODE ***/!!!
CREATE OR ALTER FUNCTION odd_or_even_number (NUMBER INT)
RETURNS NUMBERS TABLE (
number_type VARCHAR(15))
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
BEGIN
IF ((@number % 2) = 0)
BEGIN
INSERT @numbers SELECT 'Even'
END
ELSE
BEGIN
INSERT @numbers SELECT 'Odd'
END
RETURN
END
SELECT * FROM odd_or_even_number(9);;
NUMBER_TYPE|
------------------+
Odd|
Inserts multiple according to if/else statement¶
The example below inserts more than one value into the table and more than one variable is modified according to the condition. Returns the table with the new values
Transact-SQL¶
CREATE OR ALTER FUNCTION new_employee_hired(@id VARCHAR (50), @position VARCHAR(50), @experience VARCHAR(15))
RETURNS @new_employee TABLE (id_employee VARCHAR (50), working_from_home BIT, team VARCHAR(15), computer VARCHAR(15))
AS
BEGIN
DECLARE @wfh BIT
DECLARE @team VARCHAR(15)
DECLARE @computer VARCHAR(15)
IF @position = 'DEVELOPER'
BEGIN
SET @team = 'TEAM_1'
SET @computer = 'LAPTOP'
END
IF @position = 'IT'
BEGIN
SET @team = 'TEAM_2'
SET @computer = 'DESKTOP'
END
IF @experience = 'JUNIOR'
BEGIN
SET @wfh = '0'
END
IF @experience = 'SENIOR'
BEGIN
SET @wfh = '1'
END
INSERT INTO @new_employee VALUES (@id, @wfh, @team, @computer)
RETURN
END
SELECT * FROM new_employee_hired('123456789', 'DEVELOPER', 'SENIOR');
ID_EMPLOYEE| WORKING_FROM_HOME| TEAM| COMPUTER|
--------------+-------------------|---------|-----------|
123456789| 1| TEAM_1| LAPTOP|
Snowflake¶
!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'TABLE VALUED FUNCTIONS' NODE ***/!!!
CREATE OR ALTER FUNCTION new_employee_hired (ID STRING, POSITION STRING, EXPERIENCE STRING)
RETURNS NEW_EMPLOYEE TABLE (
id_employee VARCHAR(50),
working_from_home BOOLEAN,
team VARCHAR(15),
computer VARCHAR(15))
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
BEGIN
DECLARE @wfh BIT
DECLARE @team VARCHAR(15)
DECLARE @computer VARCHAR(15)
IF @position = 'DEVELOPER'
BEGIN
SET @team = 'TEAM_1'
SET @computer = 'LAPTOP'
END
IF @position = 'IT'
BEGIN
SET @team = 'TEAM_2'
SET @computer = 'DESKTOP'
END
IF @experience = 'JUNIOR'
BEGIN
SET @wfh = '0'
END
IF @experience = 'SENIOR'
BEGIN
SET @wfh = '1'
END
INSERT INTO @new_employee VALUES (@id, @wfh, @team, @computer)
RETURN
END
SELECT * FROM new_employee_hired('123456789', 'DEVELOPER', 'SENIOR');;
ID_EMPLOYEE| WORKING_FROM_HOME| TEAM| COMPUTER|
--------------+-------------------|---------|-----------|
123456789| 1| TEAM_1| LAPTOP|
Warning
In case there are nested if statements and more than one variables are modified in the statements it is necessary to use a stored procedure.
Update values previously inserted¶
Updates columns values of the table into the function body and returns it with the new values.
Transact-SQL¶
CREATE OR ALTER FUNCTION get_employees_history()
RETURNS @employee_history TABLE (
department_name NVARCHAR(50),
first_name NVARCHAR(50),
last_name NVARCHAR(50),
start_date DATE,
end_date DATE,
job_title NVARCHAR(50),
months_working INT
)
BEGIN
INSERT INTO @employee_history
SELECT D.name AS department_name, P.first_name, P.last_name, EH.start_date, EH.end_date, E.job_title, 0 FROM Department D
LEFT OUTER JOIN employee_department_history EH
ON D.department_ID = EH.department_ID
INNER JOIN Employee E
ON E.business_entity_ID = EH.business_entity_ID
INNER JOIN Person P
ON P.business_entity_ID = E.business_entity_ID
UPDATE @employee_history
SET
months_working =
CASE WHEN end_date IS NULL THEN DATEDIFF(MONTH, start_date, GETDATE())
ELSE DATEDIFF(MONTH, start_date, end_date)
END
RETURN;
END;
SELECT TOP(10) * FROM get_employees_history();
DEPARTMENT_NAME| FIRST_NAME| LAST_NAME| START_DATE| END_DATE| JOB_TITLE| MONTHS_WORKING|
-------------------------------------+ ------------------+-------------------+----------------+-----------------+------------------------------------+----------------------+
Sales| Syed| Abbas| 2013-03-14| NULL| Pacific Sales Manager| 106|
Production| Kim| Abercrombie| 2010-01-16| NULL| Production Technician - WC60| 144|
Quality Assurance| Hazem| Abolrous| 2009-02-28| NULL| Quality Assurance Manager| 155|
Shipping and Receiving| Pilar| Ackerman| 2009-01-02| NULL| Shipping and Receiving Supervisor| 156|
Production| Jay| Adams| 2009-03-05| NULL| Production Technician - WC60| 154|
Information Services| François| Ajenstat| 2009-01-17| NULL| Database Administrator| 156|
Sales| Amy| Alberts| 2012-04-16| NULL| European Sales Manager| 117|
Production| Greg| Alderson| 2008-12-02| NULL| Production Technician - WC45| 157|
Quality Assurance| Sean| Alexander| 2008-12-28| NULL| Quality Assurance Technician| 157|
Facilities and Maintenance| Gary| Altman| 2009-12-02| NULL| Facilities Manager| 145|
Snowflake SQL¶
!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'TABLE VALUED FUNCTIONS' NODE ***/!!!
CREATE OR ALTER FUNCTION get_employees_history ()
RETURNS EMPLOYEE_HISTORY TABLE (
department_name VARCHAR(50),
first_name VARCHAR(50),
last_name VARCHAR(50),
start_date DATE,
end_date DATE,
job_title VARCHAR(50),
months_working INT
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
BEGIN
INSERT INTO @employee_history
SELECT D.name AS department_name, P.first_name, P.last_name, EH.start_date, EH.end_date, E.job_title, 0 FROM Department D
LEFT OUTER JOIN employee_department_history EH
ON D.department_ID = EH.department_ID
INNER JOIN Employee E
ON E.business_entity_ID = EH.business_entity_ID
INNER JOIN Person P
ON P.business_entity_ID = E.business_entity_ID
UPDATE @employee_history
SET
months_working =
CASE WHEN end_date IS NULL THEN DATEDIFF(MONTH, start_date, GETDATE())
ELSE DATEDIFF(MONTH, start_date, end_date)
END
RETURN;
END;
SELECT TOP(10) * FROM get_employees_history();;
DEPARTMENT_NAME| FIRST_NAME| LAST_NAME| START_DATE| END_DATE| JOB_TITLE| MONTHS_WORKING|
-------------------------------------+ ------------------+-------------------+----------------+-----------------+------------------------------------+----------------------+
Sales| Syed| Abbas| 2013-03-14| NULL| Pacific Sales Manager| 106|
Production| Kim| Abercrombie| 2010-01-16| NULL| Production Technician - WC60| 144|
Quality Assurance| Hazem| Abolrous| 2009-02-28| NULL| Quality Assurance Manager| 155|
Shipping and Receiving| Pilar| Ackerman| 2009-01-02| NULL| Shipping and Receiving Supervisor| 156|
Production| Jay| Adams| 2009-03-05| NULL| Production Technician - WC60| 154|
Information Services| François| Ajenstat| 2009-01-17| NULL| Database Administrator| 156|
Sales| Amy| Alberts| 2012-04-16| NULL| European Sales Manager| 117|
Production| Greg| Alderson| 2008-12-02| NULL| Production Technician - WC45| 157|
Quality Assurance| Sean| Alexander| 2008-12-28| NULL| Quality Assurance Technician| 157|
Facilities and Maintenance| Gary| Altman| 2009-12-02| NULL| Facilities Manager| 145|
Multiple return clauses¶
In the following sample there is more than one return clause, this is because depending on the situation it is not necessary to keep executing the whole function.
Transact-SQL¶
CREATE OR ALTER FUNCTION create_new_team(@team_name VARCHAR(50))
RETURNS @new_team TABLE (type VARCHAR(50), name VARCHAR(50))
AS
BEGIN
DECLARE @employees INT
SET @employees = (SELECT count(*) FROM employee)
DECLARE @type VARCHAR(15)
SET @type = 'small_team'
IF (@employees < 8)
BEGIN
INSERT @new_team VALUES (@type, @team_name)
RETURN
END
SET @type = 'big_team'
INSERT @new_team VALUES (@type, @team_name)
RETURN
END
SELECT * FROM create_new_team('Team1');
TYPE| NAME|
--------------+ --------------+
SMALL_TEAM| TEAM1|
Snowflake SQL¶
!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'TABLE VALUED FUNCTIONS' NODE ***/!!!
CREATE OR ALTER FUNCTION create_new_team (TEAM_NAME STRING)
RETURNS NEW_TEAM TABLE (
type VARCHAR(50),
name VARCHAR(50))
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
BEGIN
DECLARE @employees INT
SET @employees = (SELECT count(*) FROM employee)
DECLARE @type VARCHAR(15)
SET @type = 'small_team'
IF (@employees < 8)
BEGIN
INSERT @new_team VALUES (@type, @team_name)
RETURN
END
SET @type = 'big_team'
INSERT @new_team VALUES (@type, @team_name)
RETURN
END
SELECT * FROM create_new_team('Team1');;
TYPE| NAME|
--------------+ --------------+
SMALL_TEAM| TEAM1|
Warning
This transformation is applied when there is only one value to insert, if there is more than one value it is necessary to use a stored procedure.
Complex cases¶
The example is a complex case that uses nested if statements and inserts a value depending on the true condition.
Transact-SQL¶
CREATE OR ALTER FUNCTION vacation_status(@id VARCHAR (50))
RETURNS @status TABLE (vacation_status VARCHAR(30))
AS
BEGIN
DECLARE @hire_date DATETIME
SET @hire_date = (SELECT @hire_date FROM employee WHERE employeeId = @id)
DECLARE @vacation_hours INT
SET @vacation_hours = (SELECT count(vacation_hours) FROM employee WHERE employeeId = @id)
DECLARE @time_working INT
SET @time_working = (SELECT DATEDIFF(MONTH, @hire_date,GETDATE()))
IF (@vacation_hours > 0)
BEGIN
IF (@time_working > 3)
BEGIN
IF (@vacation_hours < 120)
BEGIN
INSERT INTO @status VALUES ('Ok')
END
IF (@vacation_hours = 120)
BEGIN
INSERT INTO @status values ('In the limit')
END
IF (@vacation_hours > 120)
BEGIN
INSERT INTO @status VALUES ('With excess')
END
END
ELSE
BEGIN
INSERT INTO @status values ('Hired recently')
END
END
ELSE
BEGIN
INSERT INTO @status values ('No hours')
END
RETURN
END
SELECT * FROM vacation_status('adventure-worksken0')
VACATION_STATUS|
-----------------+
OK|
Snowflake SQL¶
!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'TABLE VALUED FUNCTIONS' NODE ***/!!!
CREATE OR ALTER FUNCTION vacation_status (ID STRING)
RETURNS STATUS TABLE (
vacation_status VARCHAR(30))
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
BEGIN
DECLARE @hire_date DATETIME
SET @hire_date = (SELECT @hire_date FROM employee WHERE employeeId = @id)
DECLARE @vacation_hours INT
SET @vacation_hours = (SELECT count(vacation_hours) FROM employee WHERE employeeId = @id)
DECLARE @time_working INT
SET @time_working = (SELECT DATEDIFF(MONTH, @hire_date,GETDATE()))
IF (@vacation_hours > 0)
BEGIN
IF (@time_working > 3)
BEGIN
IF (@vacation_hours < 120)
BEGIN
INSERT INTO @status VALUES ('Ok')
END
IF (@vacation_hours = 120)
BEGIN
INSERT INTO @status values ('In the limit')
END
IF (@vacation_hours > 120)
BEGIN
INSERT INTO @status VALUES ('With excess')
END
END
ELSE
BEGIN
INSERT INTO @status values ('Hired recently')
END
END
ELSE
BEGIN
INSERT INTO @status values ('No hours')
END
RETURN
END
SELECT * FROM vacation_status('adventure-worksken0');
VACATION_STATUS|
-----------------+
OK|
Known Issues¶
While statements along side queries¶
The problem with this example is that there’s no way of transforming the while statement to a CTE inside the WITH clause of the main select, this forces us to transform this statement to store procedure to maintain the same logic.
Transact-SQL¶
--Additional Params: -t JavaScript
CREATE OR ALTER FUNCTION get_group_name
(@department_id INT)
RETURNS @group_names TABLE (group_name VARCHAR(15))
AS
BEGIN
DECLARE @name VARCHAR(30) = 'Another Department'
WHILE @name = 'Another Department'
BEGIN
IF (@department_id < 3)
BEGIN
SET @name = 'engineering'
END
IF @department_id = 3
BEGIN
SET @name = 'Tool Design'
END
SELECT @department_id = @department_id / 3
END
INSERT @group_names SELECT @name
RETURN
END
SELECT * FROM get_group_name(9);
GROUP_NAME|
------------------+
Tool Design|
Snowflake SQL¶
!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'TABLE VALUED FUNCTIONS' NODE ***/!!!
CREATE OR ALTER FUNCTION get_group_name
(DEPARTMENT_ID INT)
RETURNS @group_names TABLE (
group_name VARCHAR(15))
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
BEGIN
DECLARE @name VARCHAR(30) = 'Another Department'
WHILE @name = 'Another Department'
BEGIN
IF (@department_id < 3)
BEGIN
SET @name = 'engineering'
END
IF @department_id = 3
BEGIN
SET @name = 'Tool Design'
END
SELECT @department_id = @department_id / 3
END
INSERT @group_names SELECT @name
RETURN
END
SELECT * FROM get_group_name(9);;
GROUP_NAME|
------------------+
Tool Design|
Declare Cursor¶
User-defined functions cannot DECLARE, OPEN, FETCH, CLOSE or DEALLOCATE a CURSOR. Use a Stored Procedure to work with cursors.
Transact-SQL¶
--Additional Params: -t JavaScript
CREATE OR ALTER FUNCTION amount_new_specimens(@id int)
RETURNS @new_specimens TABLE (amount int)
AS
BEGIN
DECLARE @first_specimen VARCHAR(30) ;
set @first_specimen = (select name_specimen from specimen where specimen_id = @id);
DECLARE @second_specimen VARCHAR(30);
DECLARE @specimens TABLE (name_specimen VARCHAR(30))
DECLARE Cursor1 CURSOR
FOR SELECT name_specimen
FROM specimen
OPEN cursor1
FETCH NEXT FROM cursor1
INTO @second_specimen;
WHILE @@FETCH_STATUS = 0
BEGIN
IF @first_specimen <> @second_specimen
BEGIN
INSERT INTO @specimens values (CONCAT_WS('-', @first_specimen, @second_specimen))
END
FETCH NEXT FROM cursor1
INTO @second_specimen;
END
CLOSE cursor1;
DEALLOCATE cursor1;
INSERT INTO @new_specimens SELECT COUNT(*) FROM @specimens
RETURN
END
SELECT * FROM amount_new_specimens(1);
AMOUNT|
------------------+
3|
Snowflake SQL¶
--Additional Params: -t JavaScript
!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'TABLE VALUED FUNCTIONS' NODE ***/!!!
CREATE OR ALTER FUNCTION amount_new_specimens (ID INT)
RETURNS @new_specimens TABLE (
amount INT
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
BEGIN
DECLARE @first_specimen VARCHAR(30) ;
set @first_specimen = (select name_specimen from specimen where specimen_id = @id);
DECLARE @second_specimen VARCHAR(30);
DECLARE @specimens TABLE (name_specimen VARCHAR(30))
DECLARE Cursor1 CURSOR
FOR SELECT name_specimen
FROM specimen
OPEN cursor1
FETCH NEXT FROM cursor1
INTO @second_specimen;
WHILE @@FETCH_STATUS = 0
BEGIN
IF @first_specimen <> @second_specimen
BEGIN
INSERT INTO @specimens values (CONCAT_WS('-', @first_specimen, @second_specimen))
END
FETCH NEXT FROM cursor1
INTO @second_specimen;
END
CLOSE cursor1;
DEALLOCATE cursor1;
INSERT INTO @new_specimens SELECT COUNT(*) FROM @specimens
RETURN
END
SELECT * FROM amount_new_specimens(1);;
AMOUNT|
------------------+
3|
Different statements are not supported in Common Tables Expressions¶
The clauses UPDATE, INSERT, DELETE, ALTER or DROP are not supported on the body of common tables expressions, even after their declaration using a delimitator. For this reason, the function can be modified to work as a stored procedure.
Transact-SQL¶
--Additional Params: -t JavaScript
CREATE OR ALTER PROCEDURE product_history
AS
BEGIN
DECLARE @product_history TABLE (
product_name NVARCHAR(50),
rating INT
)
INSERT INTO @product_history
SELECT P.Name AS product_name, AVG(ALL R.rating) FROM Production.product P
INNER JOIN Production.product_review R
ON R.product_ID = P.product_ID
GROUP BY P.Name;
DELETE FROM @product_history
WHERE rating < 2;
SELECT * FROM @product_history;
END
GO;
EXEC product_history
PRODUCT_NAME| Rating|
----------------------------------+------------------|
HL Mountain Pedal| 3|
Mountain Bike Socks, M| 5|
Road-550-W Yellow, 40| 5|
Snowflake SQL¶
CREATE OR REPLACE PROCEDURE product_history ()
RETURNS STRING
LANGUAGE JAVASCRIPT
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
// REGION SnowConvert Helpers Code
var _RS, ROW_COUNT, _ROWS, MESSAGE_TEXT, SQLCODE = 0, SQLSTATE = '00000', OBJECT_SCHEMA_NAME = 'UNKNOWN', ERROR_HANDLERS, NUM_ROWS_AFFECTED, PROC_NAME = arguments.callee.name, DOLLAR_DOLLAR = '$' + '$';
function* sqlsplit(sql) {
var part = '';
var ismark = () => sql[i] == '$' && sql[i + 1] == '$';
for(var i = 0;i < sql.length;i++) {
if (sql[i] == ';') {
yield part + sql[i];
part = '';
} else if (ismark()) {
part += sql[i++] + sql[i++];
while ( i < sql.length && !ismark() ) {
part += sql[i++];
}
part += sql[i] + sql[i++];
} else part += sql[i];
}
if (part.trim().length) yield part;
};
var formatDate = (arg) => (new Date(arg - (arg.getTimezoneOffset() * 60000))).toISOString().slice(0,-1);
var fixBind = function (arg) {
arg = arg == undefined ? null : arg instanceof Date ? formatDate(arg) : arg;
return arg;
};
var EXEC = (stmt,binds = [],severity = "16",noCatch = false) => {
binds = binds ? binds.map(fixBind) : binds;
for(var stmt of sqlsplit(stmt)) {
try {
_RS = snowflake.createStatement({
sqlText : stmt,
binds : binds
});
_ROWS = _RS.execute();
ROW_COUNT = _RS.getRowCount();
NUM_ROWS_AFFECTED = _RS.getNumRowsAffected();
return {
THEN : (action) => !SQLCODE && action(fetch(_ROWS))
};
} catch(error) {
let rStack = new RegExp('At .*, line (\\d+) position (\\d+)');
let stackLine = error.stackTraceTxt.match(rStack) || [0,-1];
MESSAGE_TEXT = error.message.toString();
SQLCODE = error.code.toString();
SQLSTATE = error.state.toString();
snowflake.execute({
sqlText : `SELECT UPDATE_ERROR_VARS_UDF(?,?,?,?,?,?)`,
binds : [stackLine[1],SQLCODE,SQLSTATE,MESSAGE_TEXT,PROC_NAME,severity]
});
throw error;
}
}
};
// END REGION
EXEC(`CREATE OR REPLACE TEMPORARY TABLE T_product_history (
product_name VARCHAR(50),
rating INT
)`);
EXEC(` INSERT INTO T_product_history
SELECT
P.Name AS product_name,
AVG(ALL R.rating) FROM
Production.product P
INNER JOIN
Production.product_review R
ON R.product_ID = P.product_ID
GROUP BY
P.Name`);
EXEC(`DELETE FROM
T_product_history
WHERE
rating < 2`);
EXEC(`
SELECT
*
FROM
T_product_history`);
$$;
!!!RESOLVE EWI!!! /*** SSC-EWI-0040 - THE STATEMENT IS NOT SUPPORTED IN SNOWFLAKE ***/!!!
;
CALL product_history();
PRODUCT_NAME| Rating|
----------------------------------+------------------|
HL Mountain Pedal| 3|
Mountain Bike Socks, M| 5|
Road-550-W Yellow, 40| 5|
Related EWIs¶
SSC-EWI-0040: Statement Not Supported.
SSC-EWI-0073: Pending Functional Equivalence Review
SCALAR¶
Applies to
[x] SQL Server
[x] Azure Synapse Analytics
Description¶
Note
Some parts in the output code are omitted for clarity reasons.
A scalar user-defined function is a Transact-SQL or common language runtime (CLR) routine that accepts parameters, performs an action, such as a complex calculation, and returns the result of that action as a scalar value. (SQL Server Language Reference CREATE FUNCTION subsection).
Note
These functions are usually used inside the SELECTstatement, or single variable setup (most likely inside a stored procedure).
Transact-SQL Syntax¶
-- Transact-SQL Scalar Function Syntax
CREATE [ OR ALTER ] FUNCTION [ schema_name. ] function_name
( [ { @parameter_name [ AS ][ type_schema_name. ] parameter_data_type
[ = default ] [ READONLY ] }
[ ,...n ]
]
)
RETURNS return_data_type
[ WITH <function_option> [ ,...n ] ]
[ AS ]
BEGIN
function_body
RETURN scalar_expression
END
[ ; ]
Snowflake Syntax¶
Snowflake allows 3 different languages in their user defined functions:
SQL
JavaScript
Java
For now, SnowConvert will support only SQL and JavaScript as target languages.
Note
SQL user defined functions only supports one query as their body. They can read from the database, but is not allowed to write or modify it. (Scalar SQL UDFs Reference).
CREATE [ OR REPLACE ] [ SECURE ] FUNCTION <name> ( [ <arg_name> <arg_data_type> ] [ , ... ] )
RETURNS { <result_data_type> | TABLE ( <col_name> <col_data_type> [ , ... ] ) }
[ [ NOT ] NULL ]
[ { CALLED ON NULL INPUT | { RETURNS NULL ON NULL INPUT | STRICT } } ]
[ VOLATILE | IMMUTABLE ]
[ COMMENT = '<string_literal>' ]
AS '<function_definition>'
Note
JavaScript user defined functions allows multiple statements in their bodies, but cannot perform queries to the database. (Scalar JavaScript UDFs Reference)
CREATE [ OR REPLACE ] [ SECURE ] FUNCTION <name> ( [ <arg_name> <arg_data_type> ] [ , ... ] )
RETURNS { <result_data_type> | TABLE ( <col_name> <col_data_type> [ , ... ] ) }
[ [ NOT ] NULL ]
LANGUAGE JAVASCRIPT
[ { CALLED ON NULL INPUT | { RETURNS NULL ON NULL INPUT | STRICT } } ]
[ VOLATILE | IMMUTABLE ]
[ COMMENT = '<string_literal>' ]
AS '<function_definition>'
Sample Source Patterns¶
Set and Declare Statements¶
The most common statements in function bodies are the DECLARE and SET statements. For DECLARE statements without default value, the transformation will be ignored. SET statements and DECLARE statements with a default value, will be transformed to a COMMON TABLE EXPRESSION. Each common table expression will contain a column that represents the local variable value.
Transact-SQL¶
CREATE OR ALTER FUNCTION PURCHASING.GetVendorName()
RETURNS NVARCHAR(50) AS
BEGIN
DECLARE @result NVARCHAR(50)
DECLARE @BUSINESSENTITYID INT
SET @BUSINESSENTITYID = 1492
SELECT @result = Name FROM PURCHASING.VENDOR WHERE BUSINESSENTITYID = @BUSINESSENTITYID
RETURN @result
END
GO
SELECT PURCHASING.GetVendorName() as vendor_name;
vendor_name |
-----------------------+
Australia Bike Retailer|
Snowflake¶
CREATE OR REPLACE FUNCTION PURCHASING.GetVendorName ()
RETURNS VARCHAR(50)
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
$$
WITH CTE1 AS
(
SELECT
1492 AS BUSINESSENTITYID
),
CTE2 AS
(
SELECT
Name AS RESULT
FROM
PURCHASING.VENDOR
WHERE
BUSINESSENTITYID = (
SELECT
BUSINESSENTITYID
FROM
CTE1
)
)
SELECT
RESULT
FROM
CTE2
$$;
SELECT
PURCHASING.GetVendorName() as vendor_name;
VENDOR_NAME |
-----------------------+
Australia Bike Retailer|
If/Else Statement Transformation¶
If/Else statement can be handled in different ways, they can be either transformed to javascript or to SQL using the CASE EXPRESSION inside the select allowing conditionals inside the queries, while the javascript transformation is pretty straightforward, the Case statement might not be so obvious at first glance.
Transact-SQL¶
CREATE OR ALTER FUNCTION PURCHASING.HasActiveFlag(@BusinessEntityID int)
RETURNS VARCHAR(10) AS
BEGIN
DECLARE @result VARCHAR(10)
DECLARE @ActiveFlag BIT
SELECT @ActiveFlag = ActiveFlag from PURCHASING.VENDOR v where v.BUSINESSENTITYID = @BusinessEntityID
IF @ActiveFlag = 1
SET @result = 'YES'
ELSE IF @ActiveFlag = 0
SET @result = 'NO'
RETURN @result
END
GO
SELECT PURCHASING.HasActiveFlag(1516) as has_active_flag;
has_active_flag|
---------------+
NO |
Snowflake¶
CREATE OR REPLACE FUNCTION PURCHASING.HasActiveFlag (P_BUSINESSENTITYID INT)
RETURNS VARCHAR(10)
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
$$
WITH CTE1 AS
(
SELECT
ActiveFlag AS ACTIVEFLAG
from
PURCHASING.VENDOR v
where
v.BUSINESSENTITYID = P_BUSINESSENTITYID
),
CTE2 AS
(
SELECT
CASE
WHEN (
SELECT
ACTIVEFLAG
FROM
CTE1
) = 1
THEN 'YES'
WHEN (
SELECT
ACTIVEFLAG
FROM
CTE1
) = 0
THEN 'NO'
END AS RESULT
)
SELECT
RESULT
FROM
CTE2
$$;
SELECT
PURCHASING.HasActiveFlag(1516) as has_active_flag;
HAS_ACTIVE_FLAG|
---------------+
NO |
Nested Statements¶
For nested statements, the structured programming is being transformed to a single query. The statements in the control-of-flow are going to be nested in table structures in order to preserve the execution order.
Note
CASE EXPRESSIONS only can return one value per statement
Example¶
Note
The following code in both programming paradigms is functionally equivalent.
DECLARE @VendorId AS int;
DECLARE @AccountNumber AS VARCHAR(50);
SELECT @VendorId = poh.VendorID
FROM Purchasing.PurchaseOrderHeader poh
WHERE PurchaseOrderID = 1
SELECT @AccountNumber = v.AccountNumber
FROM Purchasing.Vendor v
WHERE v.BusinessEntityID = @VendorId
SELECT V.AccountNumber AccountNumber
FROM (SELECT poh.VendorID VendorId
FROM Purchasing.PurchaseOrderHeader poh
WHERE PurchaseOrderID = 1
) T1, Purchasing.Vendor v
WHERE v.BusinessEntityID = T1.VendorId
AccountNumber|
-------------+
LITWARE0001 |
Conditional variables through SELECTs¶
Variable definition and assignment within conditional statements tends to be somewhat problematic, because references to the variable further down the code would have to know where the variable was last modified. Not only that, but if the reference is within another conditional statement, then there would have to be some kind of redirect that references the previous known assignment to the variable.
This is all aggravated by nesting and complex querying that can be found on input code.
In the following scenario, the first IF statement can be transformed without problems, because the contents are straightforward enough. The second and third IF statements are commented out because they’re not supported at the moment, since there are statements other than variable assignments through SELECT.
SQL Server¶
CREATE or ALTER FUNCTION PURCHASING.SELECTINUDF (
@param1 varchar(12)
)
RETURNS int
AS
BEGIN
declare @var1 int;
declare @var2 int;
declare @var3 int;
IF @param1 = 'first'
BEGIN
select @var1 = col1 + 10 from table1 WHERE id = 0;
select @var2 = col1 + 20 from table1 WHERE id = 0;
select @var3 = col1 + 30 from table1 WHERE id = 0;
END
IF @param1 = 'second'
BEGIN
declare @var4 int = 10;
select @var1 = col1 + 40 from table1 WHERE id = 0;
select @var2 = col1 + 40 from table1 WHERE id = 0;
END
IF @param1 = 'third'
BEGIN
select col1 from table1 where id = 0;
select @var1 = col1 + 50 from table1 WHERE id = 0;
select @var2 = col1 + 50 from table1 WHERE id = 0;
END
RETURN @var1
END
SELECT PURCHASING.SELECTINUDF('first') as result; -- Assuming table1.col1 is 0 when ID = 0
RESULT|
------+
10|
Snowflake¶
CREATE OR REPLACE FUNCTION PURCHASING.SELECTINUDF (PARAM1 STRING)
RETURNS INT
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
$$
WITH CTE1 AS
(
SELECT
CASE
WHEN PARAM1 = 'first'
THEN (SELECT
col1 + 10 AS VAR1 from
table1
WHERE
id = 0)
END AS VAR1,
CASE
WHEN PARAM1 = 'first'
THEN (SELECT
col1 + 20 AS VAR2 from
table1
WHERE
id = 0)
END AS VAR2,
CASE
WHEN PARAM1 = 'first'
THEN (SELECT
col1 + 30 AS VAR3 from
table1
WHERE
id = 0)
END AS VAR3
),
!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'IF STATEMENT' NODE ***/!!!
CTE2 AS
(
/* IF @param1 = 'second'
BEGIN
declare @var4 int = 10;
select @var1 = col1 + 40 from table1 WHERE id = 0;
select @var2 = col1 + 40 from table1 WHERE id = 0;
END*/
SELECT
null
),
!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'IF STATEMENT' NODE ***/!!!
CTE3 AS
(
/* IF @param1 = 'third'
BEGIN
select col1 from table1 where id = 0;
select @var1 = col1 + 50 from table1 WHERE id = 0;
select @var2 = col1 + 50 from table1 WHERE id = 0;
END*/
SELECT
null
),
CTE4 AS
(
SELECT
PURCHASING.SELECTINUDF('first') as result
)
SELECT
VAR1
FROM
CTE4
$$ -- Assuming table1.col1 is 0 when ID = 0
;
RESULT|
------+
10|
Assign and return a variable¶
In this simple pattern, there is a variable declaration, then, that variable is set using a SELECT statement and finally returned. This is going to be migrated to a Common Table Expression in order to keep the original behavior.
SQL Server¶
CREATE OR ALTER FUNCTION Purchasing.GetTotalFreight()
RETURNS MONEY AS
BEGIN
DECLARE @Result MONEY
SELECT @Result = ISNULL(SUM(t.Freight), 0) from Purchasing.PurchaseOrderHeader t
return @Result
END
GO
select Purchasing.GetTotalFreight() as Result;
Result |
------------+
1583978.2263|
Snowflake¶
CREATE OR REPLACE FUNCTION Purchasing.GetTotalFreight ()
RETURNS NUMBER(38, 4)
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
$$
WITH CTE1 AS
(
SELECT
NVL(SUM(t.Freight), 0) AS RESULT from
Purchasing.PurchaseOrderHeader t
)
SELECT
RESULT
FROM
CTE1
$$;
select
Purchasing.GetTotalFreight() as Result;
RESULT |
------------+
1583978.2263|
Multiple Function Calls¶
For this specific pattern there are no obvious queries, but there are multiple calls to multiple functions working on the same variable and returning it at the end. Since Snowflake only supports queries inside its functions, the solution for this block is going to be adding it to a Select and nesting the calls inside, making sure the return value is the same as the one on the source.
SQL Server¶
CREATE OR ALTER FUNCTION PURCHASING.Foo
(
@PARAM1 INT
)
RETURNS varchar(25)
AS
BEGIN
DECLARE @filter INT = @PARAM1
DECLARE @NAME VARCHAR(25) = (SELECT Name from Purchasing.Vendor v where BusinessEntityID = @filter)
SET @NAME = REPLACE(@NAME, 'Australia', 'USA')
SET @NAME = REPLACE(@NAME, 'Bike', 'Car')
RETURN @NAME
END
GO
SELECT PURCHASING.Foo(1492) AS Name;
Name |
----------------+
USA Car Retailer|
Snowflake¶
CREATE OR REPLACE FUNCTION PURCHASING.Foo (PARAM1 INT)
RETURNS VARCHAR(25)
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
$$
WITH CTE1 AS
(
SELECT
PARAM1 AS FILTER
),
CTE2 AS
(
SELECT
(SELECT
Name
from
Purchasing.Vendor v
where
BusinessEntityID = (
SELECT
FILTER
FROM
CTE1
)
) AS NAME
),
CTE3 AS
(
SELECT
REPLACE((
SELECT
NAME
FROM
CTE3
), 'Australia', 'USA') AS NAME
),
CTE4 AS
(
SELECT
REPLACE((
SELECT
NAME
FROM
CTE4
), 'Bike', 'Car') AS NAME
)
SELECT
NAME
FROM
CTE4
$$;
SELECT
PURCHASING.Foo(1492) AS Name;
NAME |
----------------+
USA Car Retailer|
Increase a variable based on multiple IF conditions and return its value¶
For this pattern, a variable is modified (increased in this case) using multiple IF conditions. In the beginning, a set of variables is initialized and used to determine whether the result variable should be increased or not. Finally, the result variable is returned.
SQL Server¶
CREATE OR ALTER FUNCTION PURCHASING.FOO()
RETURNS MONEY
AS
BEGIN
declare @firstValue MONEY
declare @secondValue MONEY
declare @Result MONEY
select @Result = 0
select @firstValue = SubTotal from Purchasing.PurchaseOrderHeader where PurchaseOrderID = 1
select @secondValue = SubTotal from Purchasing.PurchaseOrderHeader where PurchaseOrderID = 2
if @firstValue is not null
select @Result = @Result + @firstValue
if @secondValue is not null
select @Result = @Result + @secondValue
return @Result
END
GO
SELECT PURCHASING.Foo() AS Result;
Result |
--------+
473.1415|
Snowflake¶
CREATE OR REPLACE FUNCTION PURCHASING.FOO ()
RETURNS NUMBER(38, 4)
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
$$
WITH CTE1 AS
(
select
0 AS RESULT
),
CTE2 AS
(
select
SubTotal AS FIRSTVALUE
from
Purchasing.PurchaseOrderHeader
where
PurchaseOrderID = 1
),
CTE3 AS
(
select
SubTotal AS SECONDVALUE
from
Purchasing.PurchaseOrderHeader
where
PurchaseOrderID = 2
),
CTE4 AS
(
SELECT
CASE
WHEN (
SELECT
FIRSTVALUE
FROM
CTE2
) is not null
THEN (
select
(
SELECT
RESULT
FROM
CTE1
) + (
SELECT
FIRSTVALUE
FROM
CTE2
) AS RESULT)
END AS RESULT
),
CTE5 AS
(
SELECT
CASE
WHEN (
SELECT
SECONDVALUE
FROM
CTE3
) is not null
THEN (
select
(
SELECT
RESULT
FROM
CTE1
) + (
SELECT
SECONDVALUE
FROM
CTE3
) AS RESULT)
ELSE (SELECT
RESULT
FROM
CTE4)
END AS RESULT
)
SELECT
RESULT
FROM
CTE5
$$;
SELECT
PURCHASING.Foo() AS Result;
RESULT |
--------+
473.1415|
Two or more RETURN statements¶
For this pattern, the IF block containing the return clause that breaks the code flow is added at the end of the body, like the final statement to be executed in a CASE expression.
Basic Case¶
For this particular scenario, there is no logic between the conditional RETURN statement and the final RETURN statement, so all body will be mapped to a single CASE EXPRESSION.
SQL Server¶
CREATE OR ALTER FUNCTION [PURCHASING].[FOO] ()
RETURNS INT
AS
BEGIN
IF exists (SELECT PreferredVendorStatus FROM Purchasing.Vendor v )
RETURN 1
RETURN 0
END
GO
SELECT PURCHASING.FOO() as result;
result|
------+
1|
Snowflake¶
CREATE OR REPLACE FUNCTION PURCHASING.FOO ()
RETURNS INT
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
$$
SELECT
CASE
WHEN exists (SELECT
PreferredVendorStatus
FROM
Purchasing.Vendor v
)
THEN 1
ELSE 0
END
$$;
SELECT
PURCHASING.FOO() as result;
RESULT|
------+
1|
Common Table Expressions¶
Common table expressions will be kept as in the original code, and they are going to be concatenated with the generated ones. SnowConvert is able to identify first all the original COMMON TABLE EXPRESSION names in order to avoid generating duplicated names.
SQL Server¶
CREATE OR ALTER FUNCTION [PURCHASING].[FOO]
(
@status INT
)
Returns INT
As
Begin
Declare @result as int = 0
;WITH ctetable(RevisionNumber) as
(
SELECT RevisionNumber
FROM Purchasing.PurchaseOrderHeader poh
where poh.Status = @status
),
finalCte As
(
SELECT RevisionNumber FROM ctetable
)
Select @result = count(RevisionNumber) from finalCte
return @result;
End
GO
SELECT PURCHASING.FOO(4) as result;
result|
------+
3689|
Snowflake¶
CREATE OR REPLACE FUNCTION PURCHASING.FOO (STATUS INT)
Returns INT
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
AS
$$
WITH CTE1 AS
(
SELECT
0 AS RESULT
),
ctetable (
RevisionNumber
) as
(
SELECT
RevisionNumber
FROM
Purchasing.PurchaseOrderHeader poh
where
poh.Status = STATUS
),
finalCte As
(
SELECT
RevisionNumber
FROM
ctetable
),
CTE2 AS
(
Select
COUNT(RevisionNumber) AS RESULT from
finalCte
)
SELECT
RESULT
FROM
CTE2
$$;
SELECT
PURCHASING.FOO(4) as result;
RESULT|
------+
3689|
Transform to JavaScript UDFs¶
If there are multiple statements and the function does not access the database in any way, it can be transformed into a JavaScript function keeping the functional equivalence
SQL Server¶
CREATE OR ALTER FUNCTION PURCHASING.GetFiscalYear
(
@DATE AS DATETIME
)
RETURNS INT
AS
BEGIN
DECLARE @FiscalYear AS INT
DECLARE @CurMonth AS INT
SET @CurMonth = DATEPART(M,@DATE)
SET @FiscalYear = DATEPART(YYYY, @DATE)
IF (@CurMonth >= 7)
BEGIN
SET @FiscalYear = @FiscalYear + 1
END
RETURN @FiscalYear
END
GO
SELECT PURCHASING.GetFiscalYear('2020-10-10') as DATE;
CREATE OR ALTER FUNCTION PURCHASING.[getCleanChargeCode]
(
@ChargeCode varchar(50)
)
returns varchar(50) as
begin
declare @CleanChargeCode varchar(50),@Len int,@Pos int=2
set @Pos=LEN(@ChargeCode)-1
while @Pos > 1
begin
set @CleanChargeCode=RIGHT(@ChargeCode,@Pos)
if TRY_CAST(@CleanChargeCode as bigint) is not null
return @CleanChargeCode
set @Pos=@Pos-1
end
set @Pos=LEN(@ChargeCode)-1
while @Pos > 1
begin
set @CleanChargeCode=LEFT(@ChargeCode,@Pos)
if TRY_CAST(@CleanChargeCode as bigint) is not null
return @CleanChargeCode
set @Pos=@Pos-1
end
return null
end
GO
SELECT PURCHASING.[getCleanChargeCode]('16test') AS CleanChargeCode;
DATE|
----+
2021|
CleanChargeCode|
---------------+
16 |
Snowflake¶
--** SSC-FDM-0029 - USER DEFINED FUNCTION WAS TRANSFORMED TO SNOWFLAKE PROCEDURE **
CREATE OR REPLACE PROCEDURE PURCHASING.GetFiscalYear (DATE TIMESTAMP_NTZ(3))
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
DECLARE
FISCALYEAR INT;
CURMONTH INT;
BEGIN
CURMONTH := DATE_PART(month, :DATE :: TIMESTAMP);
FISCALYEAR := DATE_PART(year, :DATE :: TIMESTAMP);
IF ((:CURMONTH >= 7)) THEN
BEGIN
FISCALYEAR := :FISCALYEAR + 1;
END;
END IF;
RETURN :FISCALYEAR;
END;
$$;
SELECT
!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'GetFiscalYear' NODE ***/!!!
PURCHASING.GetFiscalYear('2020-10-10') as DATE;
--** SSC-FDM-0029 - USER DEFINED FUNCTION WAS TRANSFORMED TO SNOWFLAKE PROCEDURE **
CREATE OR REPLACE PROCEDURE PURCHASING.getCleanChargeCode (CHARGECODE STRING)
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
DECLARE
CLEANCHARGECODE VARCHAR(50);
LEN INT;
POS INT := 2;
BEGIN
POS := LEN(:CHARGECODE)-1;
WHILE (:POS > 1) LOOP
CLEANCHARGECODE := RIGHT(:CHARGECODE, :POS);
IF (TRY_CAST(:CLEANCHARGECODE as BIGINT) is not null) THEN
RETURN :CLEANCHARGECODE;
END IF;
POS := :POS -1;
END LOOP;
POS := LEN(:CHARGECODE)-1;
WHILE (:POS > 1) LOOP
CLEANCHARGECODE := LEFT(:CHARGECODE, :POS);
IF (TRY_CAST(:CLEANCHARGECODE as BIGINT) is not null) THEN
RETURN :CLEANCHARGECODE;
END IF;
POS := :POS -1;
END LOOP;
RETURN null;
END;
$$;
SELECT
PURCHASING.getCleanChargeCode('16test') !!!RESOLVE EWI!!! /*** SSC-EWI-0067 - UDF WAS TRANSFORMED TO SNOWFLAKE PROCEDURE, CALLING PROCEDURES INSIDE QUERIES IS NOT SUPPORTED ***/!!! AS CleanChargeCode;
DATE |
------+
2021.0|
CLEANCHARGECODE|
---------------+
16 |
Known Issues¶
Warning
User-defined functions cannot be used to perform actions that modify the database state
Warning
User-defined functions cannot contain an OUTPUT INTO clause that has a table as its target
Warning
User-defined functions cannot DECLARE, OPEN, FETCH, CLOSE or DEALLOCATE a CURSOR. Use a Stored Procedure if you need to use cursors.
Warning
User-defined functions cannot perform control-of-flow statements such as WHILE if there is at least one call to the database
Warning
User-defined functions with references to other user-defined functions that were transformed to Stored Procedures, will be transformed to Stored Procedures too.
Warning
User-defined functions that use @@ROWCOUNT are not supported in SQL and should be transformed to stored procedures in order to keep the functional equivalence.
Warning
User-defined functions that have SELECT statements assigning a variable to itself is not supported in Snowflake. See also SELECT @local_variable
For all the unsupported cases, please check the related EWIs and the patterns below to obtain recommendations and possible workarounds.
Conditionals other than if/else statements along side queries¶
The next scenario involves the use of the “while statement” along side other queries. The problem with this example is that there’s no way of transforming the while statement to a CTE inside the WITH clause of the main select, this forces us to transform this statement to JavaScript procedure to maintain the same logic.
SQL Server¶
CREATE OR ALTER FUNCTION PURCHASING.FOO()
RETURNS INT
AS
BEGIN
DECLARE @i int = 0, @p int;
Select @p = COUNT(*) FROM PURCHASING.VENDOR
WHILE (@p < 1000)
BEGIN
SET @i = @i + 1
SET @p = @p + @i
END
IF (@i = 6)
RETURN 1
RETURN @p
END
GO
SELECT PURCHASING.FOO() as result;
result|
------+
1007|
Snowflake
--** SSC-FDM-0029 - USER DEFINED FUNCTION WAS TRANSFORMED TO SNOWFLAKE PROCEDURE **
CREATE OR REPLACE PROCEDURE PURCHASING.FOO ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
DECLARE
I INT := 0;
P INT;
BEGIN
Select
COUNT(*)
INTO
:P
FROM
PURCHASING.VENDOR;
WHILE (:P < 1000) LOOP
I := :I + 1;
P := :P + :I;
END LOOP;
IF ((:I = 6)) THEN
RETURN 1;
END IF;
RETURN :P;
END;
$$;
SELECT
PURCHASING.FOO() !!!RESOLVE EWI!!! /*** SSC-EWI-0067 - UDF WAS TRANSFORMED TO SNOWFLAKE PROCEDURE, CALLING PROCEDURES INSIDE QUERIES IS NOT SUPPORTED ***/!!! as result;
FOO |
----+
1007|
Assign a variable using its own value iterating through a rowset¶
In the following example, the variable @names is used to concatenate multiple values from a column into one single string. The variable is updated on each iteration as shown, which is not supported by SnowFlake UDFs. For this scenario, the function should be transformed into a procedure.
SQL Server
CREATE OR ALTER FUNCTION PURCHASING.FOO()
RETURNS VARCHAR(8000)
AS
BEGIN
DECLARE @names varchar(8000)
SET @names = ''
SELECT @names = ISNULL(@names + ' ', '') + Name from Purchasing.Vendor v
return @names
END
GO
select PURCHASING.FOO() as names;
names |
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
Australia Bike Retailer Allenson Cycles Advanced Bicycles Trikes, Inc. Morgan Bike Accessories Cycling Master Chicago Rent-All Greenwood Athletic Company Compete Enterprises, Inc International Light Speed Training Systems Gardner Touring Cycles Internati|
Snowflake query
--** SSC-FDM-0029 - USER DEFINED FUNCTION WAS TRANSFORMED TO SNOWFLAKE PROCEDURE **
CREATE OR REPLACE PROCEDURE PURCHASING.FOO ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
DECLARE
NAMES VARCHAR(8000);
BEGIN
NAMES := '';
SELECT
NVL(:NAMES || ' ', 0) + Name
INTO
:NAMES
from
Purchasing.Vendor v;
RETURN :NAMES;
END;
$$;
select
PURCHASING.FOO() !!!RESOLVE EWI!!! /*** SSC-EWI-0067 - UDF WAS TRANSFORMED TO SNOWFLAKE PROCEDURE, CALLING PROCEDURES INSIDE QUERIES IS NOT SUPPORTED ***/!!! as names;
Warning
For the described scenarios above, consider the following limitations:
All the calls to user-defined functions in DML queries such as
SELECT,INSERT,DELETE,UPDATEorMERGEwill fail because calls to Stored Procedures within these queries are not allowed.Calls to user-defined functions inside procedures, should be preceeded by the
CALLkeyword.Use- defined functions used in COMPUTED COLUMNS will fail during the execution.
Related EWIs¶
SSC-EWI-0067: UDF was transformed to Snowflake procedure, calling procedures inside a query is not supported.
SSC-EWI-0073: Pending Functional Equivalence Review.
SSC-FDM-0029: User defined function was transformed to a Snowflake procedure.