mean aggregate function

Applies to: check marked yes Databricks SQL check marked yes Databricks Runtime

Returns the mean calculated from values of a group. This function is a synonym for avg aggregate function.

Syntax 

mean ( [ALL | DISTINCT] expr ) [FILTER ( WHERE cond ) ]

This function can also be invoked as a window function using the OVER clause.

Arguments

  • expr: An expression that evaluates to a numeric.

  • cond: An optional boolean expression filtering the rows used for aggregation.

Returns

The result type is computed as for the arguments:

  • DECIMAL(p, s): The result type is a` DECIMAL(p + 4, s + 4)`. If the maximum precision for DECIMAL is reached, the increase in scale is limited to avoid loss of significant digits.

  • year-month interval: The result is an INTERVAL YEAR TO MONTH.

  • day-time interval: The result is an INTERVAL DAY TO SECOND.

  • In all other cases the result is a DOUBLE.

Nulls within the group are ignored. If a group is empty or consists only of nulls the result is NULL.

If DISTINCT is specified the mean is computed after duplicates have been removed.

Warning

In Databricks Runtime, if spark.sql.ansi.enabled is false, an overflow returns NULL instead of an error.

Examples 

> SELECT mean(col) FROM VALUES (1), (2), (3) AS tab(col);
 2.0

> SELECT mean(DISTINCT col) FROM VALUES (1), (1), (2), (NULL) AS tab(col);
 1.5

> SELECT mean(col) FROM VALUES (1), (2), (NULL) AS tab(col);
 1.5