Categories:: Data metric functions

NULL_PERCENT (system data metric function)¶

Returns the percentage of columns values that are NULL for the specified column 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.NULL_PERCENT(<query>)

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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 NUMBER value.

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.

Example¶

Measure the percent of NULL values for the SSN column (i.e. US social security number):

SELECT SNOWFLAKE.CORE.NULL_PERCENT(
  SELECT
    ssn
  FROM hr.tables.empl_info
);

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+----------------------------------------------------------------+
| SNOWFLAKE.CORE.NULL_COUNT(SELECT ssn FROM hr.tables.empl_info) |
+----------------------------------------------------------------+
| 1                                                              |
+----------------------------------------------------------------+