VAR_POP is an aggregate function that evaluates the population variance of an expression over a set of rows.
See Aggregates (set functions) for more information about these functions.
VAR_POP is allowed only on expressions that evaluate to numeric data types.
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).
Population variance is calculated as follows:
sum(xi2)/n - m2 where n is the number of items in the population m is the population average x1 ... xn are the items in the population
-- find the variance in flight time per aircraft SELECT AIRCRAFT, VAR_POP( flying_time ) FROM flights GROUP BY aircraft;