MySql selecting default value if there are no results?

Question

i\'m having 2 tables: members and comments. I select all members, and then join comments. But in comments I\'m selecting some SUM of points, and if user never commented, I can\'

Answer 1

I'm not sure why you are including the comment_id in your SELECT list if you just want users and their rankings. Do you want only their ranking on that particular comment? I'll give a solution for now that assumes you just want a full member list with rankings:

SELECT
    M.member_id,
    M.user_id,
    M.avatar,
    COALESCE(SUM(C.vote_value), 0) AS vote_value_sum,
    COALESCE(SUM(C.best), 0) AS best_sum,
    COALESCE(SUM(C.vote_value), 0) + SUM(C.best) * 10 AS total_value
FROM
    Members M
LEFT OUTER JOIN Comments C ON
    C.author_id = M.member_id
GROUP BY
    M.member_id
ORDER BY
    total_value DESC
LIMIT 0, 20

(this assumes that vote_value and best are NOT NULL columns or that MySQL will disregard those when calculating SUM values - I believe that it does, but I haven't tested that)