Categories:

Aggregate functions (General) , Window function syntax and usage (General)

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> )
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Window function

VARIANCE( [ DISTINCT ] <expr1> ) OVER (
                                      [ PARTITION BY <expr2> ]
                                      [ ORDER BY <expr3> [ ASC | DESC ] [ <window_frame> ] ]
                                      )
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For detailed window_frame syntax, see Window function 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 this function is called as a window function with an OVER clause that contains an ORDER BY clause:

    • A window frame is required. If no window frame is specified explicitly, the following implied window frame is used:

      RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW

      For more information about window frames, including syntax, usage notes, and examples, see Window function syntax and usage.

    • Using the keyword DISTINCT inside the window function is prohibited and results in a compile-time error.

Examples¶

For examples, see VAR_SAMP.

Language: English