VAR_POP function

VAR_POP function VAR_POP is an aggregate function that evaluates the population variance of an expression over a set of rows. VAR_POP aggregate function

See for more information about these functions.

VAR_POP is allowed only on expressions that evaluate to numeric data types.

Syntax VAR_POP ( expression )

The expression can contain multiple column references or expressions, but it cannot contain another aggregate or subquery. It must evaluate to a built-in numeric data type. If an expression evaluates to NULL, the aggregate skips that value.

The resulting data type is DOUBLE (it might overflow).

Formula

Population variance is calculated as follows:

sum(x_i²)/n - m² where n is the number of items in the population m is the population average x₁ ... x_n are the items in the population Example -- find the variance in flight time per aircraft SELECT AIRCRAFT, VAR_POP( flying_time ) FROM flights GROUP BY aircraft;