Categories:: Data metric functions

NAN_PERCENT (system data metric function)¶

Returns the percentage of column values that are NaN (not a number). The percentage is computed over the total row count, including NULL values in the denominator.

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.

Syntax¶

SNOWFLAKE.CORE.NAN_PERCENT(<query>)

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:

FLOAT
VARCHAR

Returns¶

The function returns a FLOAT value. The function returns NULL if the table or view has no rows.

Usage notes¶

For a FLOAT column, the function counts the IEEE 754 NaN value. Infinity and negative infinity are not counted.
For a VARCHAR column, the function counts the text NaN. The match is case-insensitive and ignores leading and trailing ASCII whitespace.

Example¶

Measure the percentage of NaN values in the reading column:

SELECT SNOWFLAKE.CORE.NAN_PERCENT(
  SELECT
    reading
  FROM iot.tables.sensor_readings
);