Term: STDDEV_POP

Definition:
In Oracle PL/SQL, STDDEV_POP is a built in function which returns the population standard deviation of a set of numbers i.e. square root of the population variance for the input number set. It can be used as both an Aggregate and an Analytic function.

Example Syntax:

Aggregate Function:

STDDEV_POP( [ DISTINCT | ALL ] expression )

Analytic Function:

STDDEV_POP( [ DISTINCT | ALL ] expression ) [ OVER ( analytical_clause ) ]

Example Usage:

The SQL statement below returns the population standard deviation of the Quantity field from ORDERS table:

SELECT STDDEV_POP(QTY)

FROM ORDERS;



STDDEV_POP(QTY)

---------------

     143.910403

The SQL statement below returns the cumulative population standard deviation of the quantity over the orders against each date.

SELECT DT,STDDEV_POP(QTY) OVER (ORDER BY dt)

FROM ORDERS





DT        STDDEV_POP(QTY)OVER(ORDERBYDT)

--------- ------------------------------

20-OCT-10                              0

01-NOV-10                             75

09-DEC-10                     62.3609564

13-JAN-11                     138.021737

15-JAN-11                     147.105404

16-JAN-11                     145.459043

18-JAN-11                     143.910403



7 rows selected.