STDDEV_POP Function [Aggregate]

Computes the standard deviation of a population consisting of a numeric-expression, as a DOUBLE.

Syntax

STDDEV_POP ( [ ALL ] expression )

Parameters

Parameter	Description
expression	The expression (commonly a column name) whose population-based standard deviation is calculated over a set of rows.

Returns

DOUBLE

Examples

The following statement lists the average and variance in the number of items per order in different time periods:

SELECT year( ship_date ) AS Year, quarter( ship_date )
  AS Quarter, AVG( quantity ) AS Average, 
  STDDEV_POP ( quantity ) AS Variance 
FROM SalesOrderItems GROUP BY Year, Quarter 
  ORDER BY Year, Quarter;

Year	Quarter	Average	Variance
2000	1	25.775148	14.2794
2000	2	27.050847	15.0270
...	...	...	...

Usage

Computes the population standard deviation of the provided value expression evaluated for each row of the group or partition (if DISTINCT was specified, then each row that remains after duplicates have been eliminated), defined as the square root of the population variance.

Standards and Compatibility

SQL—Vendor extension to ISO/ANSI SQL grammar.
Sybase—Not supported by Adaptive Server Enterprise.