STDEVP

Syntax

SELECT STDEVP(stlpec) FROM tabulka;

Popis

Príkaz jazyka SQL

The aggregate function STDEVP computes the standard deviation for the population of all the values listed in a column or expression.

STDEVP is used when the group of numbers being evaluated is complete - it's the entire population of values. In this case, the 1 is NOT subtracted and the denominator for dividing the sum of squared deviations is simply N itself, the number of observations ( a count of items in the data set ). Technically, this is referred to as "biased." Remembering that the P in STDEVP stands for "population" may be helpful. Since the data set is not a mere sample, but constituted of ALL the actual values, this standard deviation function can return a more precise result.

Príklad

> SELECT * FROM employee;

id    first_name last_name salary    start_Date   region    city managerid
------ ---------- ---------- ------------ ----------   -------- ------------- -----------
   1 Jason Martin 5890.00 2005-03-22   North Vancouver    3
   2 Alison    Mathews    4789.00 2003-07-21   South Utown    4
   3 James Smith    6678.00 2001-12-01   North Paris    5
   4 Celia Rice 5567.00 2006-03-03   South London 6
   5 Robert    Black    4467.00 2004-07-02   East    Newton 7
   6 Linda Green    6456.00 2002-05-19   East    Calgary    8
   7 David Larry    5345.00 2008-03-18   West    New York 9
   8 James Cat    4234.00 2007-07-17   West    Regina 9
   9 Joan    Act    6123.00 2001-04-16   North Toronto 10

(9 rows affected)

SELECT STDEVP(salary) StandDevSalary FROM employee;

StandDevSalary
------------------------
819.58405590357631

Pozri aj

StDev