STDDEV

Purpose

This function returns the standard deviation within a window or group of rows. This equates to the following formula:

Syntax

stddev::=

Usage Notes

  • With DISTINCT, the function considers duplicate values of expr only once. It considers all occurrences with ALL. If the function contains neither ALL nor DISTINCT, the default is ALL.
  • If a window or group has only one row, then the result of this function is 0.

Examples

Aggregate Function

Copy 
SELECT
    department, 
   STDDEV(current_salary) STDDEV
FROM employee_table GROUP BY department;
Result
DEPARTMENT STDDEV
ACCOUNTS 10606.602
HR 14361.407

Analytic Function

Copy 
SELECT 
    id, department, hire_date, current_salary, 
    STDDEV(current_salary) OVER (PARTITION BY department ORDER BY hire_date) STDDEV 
FROM employee_table ORDER BY department, hire_date;
Result
ID DEPARTMENT HIRE_DATE CURRENT_SALARY STDDEV
2005 ACCOUNTS 2013-01-01 80000 0
2003 ACCOUNTS 2015-07-01 80000 0
2002 ACCOUNTS 2017-01-01 65000 7500
2004 ACCOUNTS 2017-01-01 70000 7500
2001 ACCOUNTS 2018-07-01 55000 10606.602
1003 HR 2014-01-01 90000 0
1002 HR 2016-01-01 70000 11547.005
1004 HR 2016-01-01 70000 11547.005
1001 HR 2018-01-01 55000 14361.407