Categories:

Data metric functions

UNIQUE_COUNT (system data metric function)¶

Returns the total number of unique non-NULL values for the specified columns in a table.

This topic provides the syntax for calling the function directly. To learn how to associate the function with a table or view so it runs at regular intervals, see Associate a DMF to automate data quality checks.

Syntax¶

SNOWFLAKE.CORE.UNIQUE_COUNT(<query>)
Copy

Arguments¶

query

Specifies a SQL query that projects a single column.

Allowed data types¶

The column projected by the query must have one of the following data types:

  • DATE

  • FLOAT

  • NUMBER

  • TIMESTAMP_LTZ

  • TIMESTAMP_NTZ

  • TIMESTAMP_TZ

  • VARCHAR

Returns¶

The function returns a scalar value with a NUMBER data type.

Access control requirements¶

Associating and running a system DMF requires the USAGE privilege on the system DMF. You can grant the SNOWFLAKE.DATA_METRIC_USER database role to give users the USAGE privilege on all system DMFs. For more information, see Grant the USAGE privilege on system DMFs.

For instructions on creating a custom role with a specified set of privileges, see Creating custom roles.

For general information about roles and privilege grants for performing SQL actions on securable objects, see Overview of Access Control.

Usage notes¶

When you call a system DMF manually, you don’t need to specify whichever allowed data type you are using. You only need to specify the query for the column that you want to measure. Snowflake matches the allowed data type for the function with the data type for the column.

Example¶

Measure the number of unique non-NULL values for the SSN column (that is, US Social Security number):

SELECT SNOWFLAKE.CORE.UNIQUE_COUNT(
  SELECT
    ssn
  FROM hr.tables.empl_info
);
Copy
+------------------------------------------------------------------+
| SNOWFLAKE.CORE.UNIQUE_COUNT(SELECT ssn FROM hr.tables.empl_info) |
+------------------------------------------------------------------+
| 42                                                               |
+------------------------------------------------------------------+
Language: English