## How to get a Product() (multiplication result) rather than a SUM() (addition result) using T-Sql

Get a summary aggregation of rows in T-Sql is easy thanks to the Sum operator:

Select Sum(Qty) From Table

Why is there no Product() aggregation operation for T-Sql? Sometimes I want the values multiplied, not added.

Luckily, some one who is much smarter in math than I, observed:

log(A * B) = log(A) + log(B)

So, summing the log, and converting back to its exponential value will yield its product.

Select CAST(EXP(SUM(LOG(Qty))) as int) as ExtendedQTY

Happy Calculating!

**UPDATE: ** The above expression seems to calculate the wrong value when the value being multiplied is a large number. For example:

Select CAST(EXP(LOG(11111)) as int) yields 11110, not 11111.

Try this instead:

DECLARE @ExtendedQty FLOAT

Select @ExtendedQTY = COALESCE(@ExtendedQTY, 1) * Table.Qty From Table

Select @ExtendedQty

As always, your feedback is welcome.

- Share This Post:
- Short Url: http://wblo.gs/cih

Posted On Wednesday, February 29, 2012 2:32 PM | Comments (1) | Filed Under [ SQL ]