STDDEV_POP

Syntax

For information on syntax and semantics, see "Analytic Functions".

Purpose

STDDEV_POP computes the population standard deviation and returns the square root of the population variance. You can use it as both an aggregate and analytic function.

The expr is a number expression, and the function returns a value of type NUMBER. This function is same as the square root of the VAR_POP function. When VAR_POP returns null, this function returns null.

See Also: "Aggregate Functions" and "VAR_POP".

Aggregate Example

The following example returns the population and sample standard deviations of profit from sales in the SALES table.

SELECT STDDEV_POP(s_profit), STDDEV_SAMP(s_profit) FROM sales;

STDDEV_POP STDDEV_SAM
---------- ----------
173.975774 177.885831

Analytic Example

The following example returns the population standard deviations of salaries in the EMP table by department:

SELECT deptno, ename, sal, 
   STDDEV_POP(sal) OVER (PARTITION BY deptno) AS pop_std
   FROM emp;

    DEPTNO ENAME             SAL    POP_STD
---------- ---------- ---------- ----------
        10 CLARK            2450 1546.14215
        10 KING             5000 1546.14215
        10 MILLER           1300 1546.14215
        20 SMITH             800 1004.73877
        20 ADAMS            1100 1004.73877
        20 FORD             3000 1004.73877
        20 SCOTT            3000 1004.73877
        20 JONES            2975 1004.73877
        30 ALLEN            1600 610.100174
        30 BLAKE            2850 610.100174
        30 MARTIN           1250 610.100174
        30 JAMES             950 610.100174
        30 TURNER           1500 610.100174
        30 WARD             1250 610.100174