Question

This is my MySQL query:

SELECT ROUND( AVG(p.votes), 2) AS 'votes', games.*
FROM games
LEFT JOIN polls p ON (p.gid = games.id)
GROUP BY games.id;

It is working fine, but if there aren’t any votes on game in the polls table – the votes field is NULL then in the result – how can I replace it so it will show 0 instead (as there are 0 rows found in the polls).

Also:

Is it possible to name my condition and then use it fe. for calculations in MySQL?

This is what I mean:

SELECT ROUND( AVG(votes), 2) AS 'votes', (votes / 50 * 100) FROM `polls`;

Will throw up an error message saying that votes is a unknown column there.

So is it possible to use the condition (as ‘votes‘) name for calculating purposes in my query?

Answer 1

First:

COALESCE(ROUND( AVG(p.votes), 2), 0)

Second :
no, not possible in the exact same statement. It’s possible if the aliased part is in a subquery.
So you have to rewrite

(COALESCE(ROUND( AVG(p.votes), 2), 0) / 50 * 100)

COALESCE and IFNULL achieve the same goal (maybe not exactly the same way), but COALESCE is ANSI SQL.