Get rows product (multiplication)

Question

SO,

The problem

I have an issue with rows multiplication. In SQL, there is a SUM() function which calculates sum for some field

Answer 1

If you need this type of calculations often, I suggest you store the signs and the logarithms in separate columns.

The signs can be stored as 1 (for positives), -1 (for negatives) and 0 (for zero.)

The logarithm can be assigned for zero as 0 (or any other value) but it should not be used in calculations.

Then the calculation would be:

SELECT 
    CASE WHEN EXISTS (SELECT 1 FROM test WHERE  AND datasign = 0)
         THEN 0
         ELSE (SELECT 1-2*(SUM(datasign=-1)%2) FROM test WHERE )
    END AS resultsign,

    CASE WHEN EXISTS (SELECT 1 FROM test WHERE  AND datasign = 0)
         THEN -1            -- undefined log for result 0
         ELSE (SELECT SUM(datalog) FROM test WHERE  AND datasign <> 0)
    END AS resultlog
  ;

This way, you have no overflow problems. You can check the resultlog if it exceeds some limits or just try to calculate resultdata = resultsign * EXP(resultlog) and see if an error is thrown.