Purpose
You can call this function to calculate the population standard deviation of numeric data to a parameter of the numeric data type. A population standard deviation is the arithmetic square root of the population variance. You can use it as an aggregate or analytic function.
Note
- When you use it as an analytic function, use the
OVERclause to define a window over the data on which the function operates. The function operates on a group of rows to return a list of values.- When you use it as an aggregate function, the function operates on a set of rows and returns a single value. You do not need to add the
OVERclause.
Syntax
STDDEV_POP( [ALL] expr) [ OVER (analytic_clause) ]
Parameters
Parameter |
Description |
|---|---|
| ALL | (Optional) Specifies all numeric columns. Default value: ALL. |
| expr | A numeric data type (NUMBER, FLOAT, BINARY_FLOAT, BINARY_DOUBLE) or an expression that can be converted to a numeric data type. |
| OVER | You can use the OVER clause to define a window over the data on which the function operates. For more information about analytic functions, see Analytic functions. |
Return types
This function returns the same value type as what you specified for the expr parameter.
Examples
Assume that you have created the table employees.
obclient> SELECT * FROM employees;
+---------------+-----------+------------+--------+
DEPARTMENT_ID LAST_NAME HIREDATE SALARY
+---------------+-----------+------------+--------+
30 Raphaely 2017-07-01 1700
30 De Haan 2018-05-01 11000
40 Errazuriz 2017-07-21 1400
50 Hartstein 2019-10-05 14000
50 Raphaely 2017-07-22 1700
50 Weiss 2019-10-05 13500
90 Russell 2019-07-11 13000
90 Partners 2018-12-01 14000
+---------------+-----------+------------+--------+
8 rows in set
Aggregate example
Calculate the population standard deviation for the salary column.
obclient> SELECT STDDEV_POP(salary) FROM employees;
+-------------------------------------------+
STDDEV_POP(SALARY)
+-------------------------------------------+
5637.250548804798333699350384281939588505
+-------------------------------------------+
1 row in set
Analytic example
Group the data records in the table by the department_id column. Return the standard deviation for the salary column.
obclient> SELECT department_id,last_name,salary,STDDEV_POP(salary) OVER (PARTITION BY department_id) AS pop_std
FROM employees
ORDER BY department_id,last_name,salary;
+---------------+-----------+--------+-------------------------------------------+
DEPARTMENT_ID LAST_NAME SALARY POP_STD
+---------------+-----------+--------+-------------------------------------------+
30 De Haan 11000 4650
30 Raphaely 1700 4650
40 Errazuriz 1400 0
50 Hartstein 14000 5684.090858606052304285807872404592677763
50 Raphaely 1700 5684.090858606052304285807872404592677763
50 Weiss 13500 5684.090858606052304285807872404592677763
90 Partners 14000 500
90 Russell 13000 500
+---------------+-----------+--------+-------------------------------------------+
8 rows in set