How to Multiply all values within a column with SQL like SUM()

Question

Lets say I have table with 1 column like this:

Col A
1
2
3
4

If I SUM it, then I will get this:

Col A
10
         


        

Answer 1

This is a complicated matter. If you want to take signs and handle zero, the expression is a bit complicated:

select (case when sum(case when a = 0 then 1 else 0 end) > 0
             then 0
             else exp(sum(log(abs(a)))) *
                  (case when sum(case when a < 0 then 1 else 0 end) % 2 = 1 then -1 else 1 end)
        end) as ProductA
from table t;

Note: you do not specify a database. In some databases you would use LN() rather than LOG(). Also the function for the modulo operator (to handle negative values) also differs by database.