Here is a simplified version of the query. The actual query contains about a dozen items in the select statement similar to this calculation.

SELECT

Param1

, Param2

, Param3

, EXP(SUM(CASE WHEN(Date BETWEEN '2007-01-01' AND '2008-01-01') THEN (LOG(1+Gains)) ELSE 0 END))-1 as CY2007PercGain

FROM myTable

GROUP BY

Param1

, Param2

, Param3

Param1, Param2, Param3, and Gains are all type DECIMAL(18,8), and Date is type DATETIME