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