STDEV function is used to perform statistical standard deviation of all values in the given expression.It can be used with numeric type columns only. Null values are ignored while performing deviation of an expression.

Syntax of STDEV function :

STDEV (expression )

Expression is avalid expression in sql sever of type numeric except bit data type.

Return type of STDEV function is float.

Example of STDEV function :

SELECT STDEV(Royalty)

FROM    Products

Output

19.0220469774936

Above example returns standard deviation of royalty column.