Question

SELECT foo FROM bar
WHERE id >= (abs(random()) % (SELECT max(id) FROM bar))
LIMIT 1;

I saw this in another answer as an alternative to ORDER BY random(). I need to make sure id would always be greater than zero. Do I have to change >= to >?

Answer 1

Since x % y returns 0 when x is a multiple of y, the answer is “Yes, your expression could return 0”.

So, if id must be greater than 0, you need to use > rather than >=. Of course, if the modulo operator didn’t return 0, you could still use > instead of >= and you’d get the same effect.