Categories:

Aggregate Functions (General) , Window Functions (General, Window frame)

VARIANCE , VARIANCE_SAMP

Returns the sample variance of non-NULL records in a group. If all records inside a group are NULL, a NULL is returned.

Aliases:

VAR_SAMP

Syntax

Aggregate function

VARIANCE( [DISTINCT] <expr1> )

Window function

VARIANCE( <expr1> ) OVER (
                         [ PARTITION BY <expr2> ]
                         [ ORDER BY <expr3> [ ASC | DESC ] [ <window_frame> ] ]
                         )

For details about window_frame syntax, see Window Frame Syntax and Usage.

Arguments

expr1

The expr1 should evaluate to one of the numeric data types.

expr2

This is the expression to partition by.

expr3

This is the expression to order by within each partition.

Returns

The data type of the returned value is NUMBER(<precision>, <scale>). The scale depends upon the values being processed.

Usage Notes

  • For single-record inputs, VAR_SAMP, VARIANCE, and VARIANCE_SAMP all return NULL. This is different from the Oracle behavior, where VAR_SAMP returns NULL for a single record and VARIANCE returns 0.

  • When passed a VARCHAR expression, this function implicitly casts the input to floating point values. If the cast cannot be performed, an error is returned.

  • When called as a window function:

    • The keyword DISTINCT is permitted syntactically, but is ignored.

    • If an ORDER BY sub-clause is used inside the OVER clause, then a window frame must be used. If no window frame is specified, then the ORDER BY implies a cumulative window frame:

      RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW

      For more details about window frames, including syntax and examples, see Window Frame Syntax and Usage.

      For more information about implied window frames, see Window Frame Usage Notes.

Examples

For examples, see VAR_SAMP.