multiply(num) aggregate function in postgresql

问题

This could be incredibly simple by the documentation is quite on it. Is there a way to aggregate columns via multiplication operator in postgresql. I know i can do count(column) or sum(column), but is there a multiply(column) or product(column) function that i can use. If not, any ideas how to achieve it.

I'm using postgres 9.1

regards, Hassan

回答1:

Sure, just define an aggregate over the base multiplication function. E.g. for bigint:

CREATE AGGREGATE mul(bigint) ( SFUNC = int8mul, STYPE=bigint );

Example:

regress=> SELECT mul(x) FROM generate_series(1,5) x;
 mul 
-----
 120
(1 row)

See CREATE AGGREGATE

来源：https://stackoverflow.com/questions/21623282/multiplynum-aggregate-function-in-postgresql