Yesterday I wrote article about SQL SERVER – Introduction to Aggregate Functions. I received one email that four of the aggregate functions are statistical function and I should write something about that. VAR, STDEVP, STDEV, VARP are statistical functions as well they absolutely fit in the definition of aggregate function as well. The usage of this function is pretty simple so instead of explaining them I will go to example right away.
SELECT VAR(Bonus) 'Variance',
STDEVP(Bonus) 'Standard Deviation',
STDEV(Bonus) 'Standard Deviation',
VARP(Bonus) 'Variance for the Population'
All the functions returns result as datatype float. VAR and VARP can only be applied to numeric well all other can be applied to all numeric data type except INT datatypes.
Reference : Pinal Dave (http://blog.SQLAuthority.com)