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STDDEV_POP

Syntax

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Description of the illustration stddev_pop.gif

See Also:

"Analytic Functions" for information on syntax, semantics, and restrictions

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.

This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument.

See Also:

Table 2-10, "Implicit Type Conversion Matrix" for more information on implicit conversion

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

See Also:

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

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