Question

I realized this issue when trying to sum upvotes AND downvotes because the value of a downvote is -1 and not 0. This causes a problem when using the SQL sum() function. For example,

vote_id   vote
  1        0
  2        1
  3        1

SELECT sum(vote) //output is 2

vote_id   vote
  1       -1
  2        1
  3        1

SELECT sum(vote) //output is 1, which is the desired output

I guess first off, my question is, is using 0, null, and 1 even make sense? Or should I should I just use -1, 0, 1?

Regardless, i’d be interested to know what the SQL query would look like to to sum up and down votes using 0, null, and 1.

Answer 1

I personally would use -1, 0 and 1.

However, 0, NULL and 1 can also be made to work:

SELECT SUM(vote * 2 - 1) ...