STDDEV_POP

Syntax

stddev_pop::=

Text description of stddev_pop

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 the same as the square root of the VAR_POP function. When VAR_POP returns null, this function returns null.

Aggregate Example

The following example returns the population and sample standard deviations of the amount of sales in the sample table sh.sales:

SELECT STDDEV_POP(amount_sold) "Pop", 
   STDDEV_SAMP(amount_sold) "Samp"
   FROM sales;

       Pop       Samp
---------- ----------
896.355151 896.355592

Analytic Example

The following example returns the population standard deviations of salaries in the sample hr.employees table by department:

SELECT department_id, last_name, salary, 
   STDDEV_POP(salary) OVER (PARTITION BY department_id) AS pop_std
   FROM employees;

DEPARTMENT_ID LAST_NAME                     SALARY    POP_STD
------------- ------------------------- ---------- ----------
           10 Whalen                          4400          0
           20 Hartstein                      13000       3500
           20 Goyal                           6000       3500
.
.
.
          100 Sciarra                         7700 1644.18166
          100 Urman                           7800 1644.18166
          100 Popp                            6900 1644.18166
          110 Higgens                        12000       1850
          110 Gietz                           8300       1850