Stored Procedures Overview¶
You can write stored procedures to extend the system with procedural code that executes SQL. In a stored procedure, you can use programmatic constructs to perform branching and looping. Once you create a stored procedure, you can reuse it multiple times.
You write a procedure’s logic – its handler – in one of the supported languages. Once you have a handler, you can create a procedure with a CREATE PROCEDURE command, then call the procedure with a CALL statement.
From a stored procedure, you can return a single value or (where supported with the handler language) tabular data. For more information about supported return types, see CREATE PROCEDURE.
To both create and call an anonymous procedure, use CALL (with Anonymous Procedure). Creating and calling an anonymous procedure does not require a role with CREATE PROCEDURE schema privileges.
A stored procedure is like a UDF, but the two differ in important ways. For more information, see Choosing whether to write a stored procedure or a user-defined function.
What is a Stored Procedure?¶
A stored procedure contains logic you write so you can call it from SQL. A stored procedure’s logic typically performs database operations by executing SQL statements.
With a stored procedure, you can also:
Dynamically create and execute SQL statements.
Execute code with the privileges of the role that owns the procedure, rather than with the privileges of the role that runs the procedure.
This allows the stored procedure owner to delegate the power to perform specified operations to users who otherwise could not do so. However, there are limitations on these owner’s rights stored procedures.
You might want to use a stored procedure to automate a task that requires multiple SQL statements and is performed frequently. For example, imagine that you want to clean up a database by deleting data older than a specified date. You can write multiple DELETE statements, each of which deletes data from a specific table. You can put all of those statements in a single stored procedure and pass a parameter that specifies the cut-off date. Then you can simply call the procedure to clean up the database. As your database changes, you can update the procedure to clean up additional tables; if there are multiple users who use the cleanup command, they can call one procedure, rather than remember every table name and clean up each table individually.
Stored Procedure Example¶
Code in the following example creates a stored procedure called
myproc with a Python handler called
create or replace procedure myproc(from_table string, to_table string, count int)
runtime_version = '3.8'
packages = ('snowflake-snowpark-python')
handler = 'run'
def run(session, from_table, to_table, count):
Code in the following example calls the stored procedure
CALL myproc('table_a', 'table_b', 5);
You write a procedure’s handler – its logic – in any of several programming languages. Each language allows you to manipulate data within the constraints of the language and its runtime environment. Regardless of the handler language, you create the procedure itself in the same way using SQL, specifying your handler and handler language.
You can write a handler in any of the following languages:
Java (using the Snowpark API)
Python (using the Snowpark API)
Scala (using the Snowpark API)
Snowflake Scripting (SQL)
You write a procedure’s handler – its logic – in any of several programming languages. Each language allows you to manipulate data within the constraints of the language and its runtime environment.
You might choose a particular language if:
You already have code in that language.
For example, if you already have a Java method that will work as a handler, and the method’s object is in a .jar file, you could copy the .jar to a stage, specify the handler as the class and method, then specify the language as Java.
The language has capabilities that others don’t have.
The language has libraries that can help you do the processing that you need to do.
When choosing a language, consider also the handler locations supported. Not all languages support referring to the handler on a stage (the handler code must instead be in-line). For more information, see Keeping Handler Code In-line or on a Stage.
In-line or staged
In-line or staged
In-line or staged
Guidelines and Constraints¶
For tips on writing stored procedures, see Working with Stored Procedures.
- Snowflake constraints:
You can ensure stability within the Snowflake environment by developing within Snowflake constraints. For more information, see Designing Handlers that Stay Within Snowflake-Imposed Constraints.
Be sure to name procedures in a way that avoids collisions with other procedures. For more information, see Naming and overloading procedures and UDFs.
Specify the arguments for your stored procedure and indicate which arguments are optional. For more information, see Defining arguments for UDFs and stored procedures.
- Data type mappings:
For each handler language, there’s a separate set of mappings between the language’s data types and the SQL types used for arguments and return values. For more about the mappings for each language, see Data Type Mappings Between SQL and Handler Languages.
- Handler languages:
For language-specific content on writing a handler, see Supported Languages.
- External network access:
You can access external network locations with external network access. You can create secure access to specific network locations external to Snowflake, then use that access from within the handler code.
- Logging and tracing:
You can record code activity by capturing log messages and trace events, storing the data in a database you can query later.
Whether you choose to have a stored procedure run with caller’s rights or owner’s rights can impact the information it has access to and the tasks it may be allowed to perform. For more information, see Understanding Caller’s Rights and Owner’s Rights Stored Procedures.
Stored procedures share certain security concerns with user-defined functions (UDFs). For more information, see the following:
You can help a procedure’s handler code execute securely by following the best practices described in Security Practices for UDFs and Procedures
Ensure that sensitive information is concealed from users who should not have access to it. For more information, see Protecting Sensitive Information with Secure UDFs and Stored Procedures
Handler Code Deployment¶
When creating a procedure, you can specify its handler – which implements the procedure’s logic – as code in-line with the CREATE PROCEDURE statement or as code external to the statement, such as compiled code packaged and copied to a stage.
For more information, see Keeping Handler Code In-line or on a Stage.
Create and Call Procedures¶
You use SQL to create and call a procedure.
Once you have written handler code, you can create a stored procedure by executing the CREATE PROCEDURE statement, specifying the procedure’s handler. For more information, see Creating a Stored Procedure.
To call a procedure, execute a SQL CALL statement that specifies the procedure. For more information, see Calling a Stored Procedure.
To create a temporary procedure that executes only once and is discarded, use WITH…CALL . For more information, see CALL (with Anonymous Procedure).