 Click here to view and discuss this page in DocCommentXchange. In the future, you will be sent there automatically.
SQL Anywhere 11.0.0 » SQL Anywhere Server - SQL Reference » Using SQL » SQL functions » Alphabetical list of functions

### STDDEV_POP function [Aggregate]

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

###### Syntax 1
`STDDEV_POP( numeric-expression )`
###### Syntax 2
`STDDEV_POP( numeric-expression ) OVER ( window-spec )`
`window-spec : see Syntax 2 instructions in the Remarks section below`
###### Parameters
• numeric-expression   The expression whose population-based standard deviation is calculated over a set of rows. The expression is commonly a column name.

###### Remarks

This function converts its argument to DOUBLE, performs the computation in double-precision floating point, and returns a DOUBLE as the result.

The population-based standard deviation (s) is computed according to the following formula:

s = [ (1/N) * SUM( xi - mean( x ) )2 ]1/2

This standard deviation does not include rows where numeric-expression is NULL. It returns NULL for a group containing no rows.

For more information about the statistical computation performed, see Mathematical formulas for the aggregate functions.

Syntax 2 represents usage as a window function in a SELECT statement. As such, elements of window-spec can be specified either in the function syntax (inline), or in conjunction with a WINDOW clause in the SELECT statement. See the window-spec definition provided in WINDOW clause.

For more information about using window functions in SELECT statements, including working examples, see Window functions.

###### Standards and compatibility
• SQL/2003   SQL foundation feature (T621) outside of core SQL.

###### Example

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

 ```SELECT YEAR( ShipDate ) AS Year, QUARTER( ShipDate ) 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...
... ... ... ...