VAR_SAMP and VAR_POP ​

Given a set of integer, decimal, or floating-point numbers, return the sample variance or population variance. The VAR_SAMP result is equivalent to the squared sample standard deviation of the same set of numbers. VAR_SAMP and VARIANCE are synonyms.

VAR_SAMP | VARIANCE (expression)
VAR_POP (expression)

The return type is either DOUBLE PRECISION (for floating-point inputs) or DECIMAL (for all other inputs).

For example:

premdb=# select avg(avg_att), var_samp(avg_att) varsamp, var_pop(avg_att) varpop 
from team where avg_att>0;
  avg   |  varsamp   |   varpop   
--------+------------+------------
 36.461 | 227.433898 | 216.062203
(1 row)

In this example, the variance results are rounded:

premdb=# select avg(avg_att), round(var_samp(avg_att)) varsamp, round(var_pop(avg_att)) varpop 
from team where avg_att>0;
  avg   | varsamp | varpop 
--------+---------+--------
 36.461 |     227 |    216
(1 row)

Note: The VARIANCE or VAR_SAMP function for an expression that consists of a single value returns NULL. The VAR_POP function for an expression that consists of a single value returns 0).

Parent topic:Aggregate Functions