Why is there no "product()" aggregate function in SQL? [duplicate]

Question

When there are Sum(), min(), max(), avg(), count() functions, can someone help understand why there is no product() built-in function. And what will be the most efficient user-implementation of this aggregate function ?

Thanks, Trinity

Answer 1

If you have exponential and log functions available, then:

PRODUCT(TheColumn) = EXP(SUM(LN(TheColumn)))

Answer 2

One can make a user-defined aggregate in SQL 2005 and up by using CLR. In Postgresql, you can do it in Postgres itself, likewise with Oracle