I'm trying to get the Product of all rows for a specific column in a grouped by query. Most examples I've found point me towards combining `exp`, `sum` and `log` exp(sum(log([Column A]))) The problem I'm having is that the column contains some zeros for values and thus I'm getting this error when zeros get passed to the `log` function: >An invalid floating point operation occurred. I thought I could work around this by using a `case` expression, but that just doesn't work the way I would think it should, as it seems to evaluate all cases... select Name, Product = case when min([Value]) = 0 then 0 when min([Value]) <> 0 then exp(sum(log(I))) -- trying to get the product of all rows in this column end from ids group by Name [SqlFiddle](http://sqlfiddle.com/#!6/5e18f/1) Given the following result set: Id Name Value _________________________________ 1 a 1 2 a 2 3 b 0 4 b 1 I would expect to get the following rows: Name Product _____________ a 2 b 0 So in summary... How do you multiply rows in a column that can contain negative or zero valued numbers?
The magic of [NULLIF] seems to do the trick for the test case in your question. Since you used a different example than in your SQL Fiddle, I don't know if that's what you want there too. CREATE TABLE dbo.Ids ( Id INT NOT NULL IDENTITY(1, 1), Value INT, Name NVARCHAR(3) ); INSERT INTO dbo.Ids ( Name, Value ) VALUES ( 'a', 1 ); INSERT INTO dbo.Ids ( Name, Value ) VALUES ( 'a', 2 ); INSERT INTO dbo.Ids ( Name, Value ) VALUES ( 'b', 0 ); INSERT INTO dbo.Ids ( Name, Value ) VALUES ( 'b', 1 ); SELECT Name, CASE WHEN MIN(Value) = 0 THEN 0 WHEN MIN(Value) > 0 THEN EXP(SUM(LOG(NULLIF(Value, 0)))) -- trying to get the product of all rows in this column END AS Product FROM Ids GROUP BY Name; Returns: Name Product a 2 b 0 --- If you need a more general solution that handles negative numbers and other edge cases, see for example [The Product Aggregate in T-SQL Versus the CLR] by Scott Burkow. One T-SQL construction from that article is: EXP(SUM(LOG(NULLIF(ABS([Value]), 0)))) * IIF(SUM(IIF([Value] = 0, 1, NULL)) > 0, 0, 1) * IIF(SUM(IIF([Value] < 0, 1, 0)) % 2 = 1, -1, 1) --- As to why your original `CASE` expression did not work as expected, from the documentation for [CASE (Transact-SQL)] (emphasis added): >You should only depend on order of evaluation of the WHEN conditions for scalar expressions (including non-correlated sub-queries that return scalars), **not for aggregate expressions**. : https://docs.microsoft.com/en-us/sql/t-sql/language-elements/nullif-transact-sql : https://www.codeproject.com/Articles/548395/The-Product-Aggregate-in-T-SQL-Versus-the-CLR : https://docs.microsoft.com/en-us/sql/t-sql/language-elements/case-transact-sql#remarks