STDDEV_POP or STDDEV aggregate function

The STDDEV_POP function returns the population standard deviation (division by n) of a set of numbers.

The schema is SYSIBM.

The formula that is used to calculate the result is logically equivalent to:

STDDEV_POP = SQRT(VAR_POP)

The argument values must each be the value of any built-in numeric data type, and their sum must be within the range of the data type of the result.

The arguments can also be a character string or graphic string data type. The string input is implicitly cast to a numeric value of DECFLOAT(34).

If the argument is DECFLOAT(n), the result of the function is DECFLOAT(34). Otherwise, the result of the function is double precision floating-point. The result can be null.

Before the function is applied to the set of values derived from the argument values, null values are eliminated. If DISTINCT is specified, redundant duplicate values are also eliminated.

If the function is applied to an empty set, the result is the null value. Otherwise, the result is the population standard deviation of the values in the set.

The order in which the values are aggregated is undefined, but every intermediate result must be within the range of the result data type.

Notes

Syntax alternatives:: STDDEV_POP should be used for conformance to the SQL standard.

Example

Using sample table DSN8C10.EMP, set the host variable DEV, which is defined as double precision floating-point, to the population standard deviation of the salaries for the employees in department 'A00' (WORKDEPT='A00').

   SELECT STDDEV_POP(SALARY)
     INTO :DEV
     FROM DSN8C10.EMP
     WHERE WORKDEPT = 'A00';

The value of DEV is set to an approximate value of 9742.43.