Question

I am running this query which selects a few fields from one table and returns counts from some other tables.

My problem: if one of my counter fields counts zero, it doesn’t return the number 0, it’s just blank – which is what I would like to try and solve.

SELECT mem.member_id, mem.screen_name, mem.firstname, mem.lastname, mem.country_code, 
mem.joined, rep.rep as reputation, com.cnt as comments FROM members AS mem
LEFT OUTER JOIN (
    SELECT member_id, SUM(awarded_what) as rep
    FROM members_reputation
    GROUP BY member_id) rep
    ON mem.member_id = rep.member_id
LEFT OUTER JOIN (
    SELECT member_id, COUNT(comment_id) as cnt
    FROM blog_comments
    GROUP BY comment_id) com
    ON mem.member_id = com.member_id
GROUP BY mem.member_id
ORDER BY mem.joined DESC

What I would like is something like this:

Screen Name      | Comments
-----------------|--------------------
marty76          | 0
jonnyBoy12       | 0
adamApple        | 12

But, I’m getting something like this instead!

Screen Name      | Comments
-----------------|--------------------
marty76          | 
jonnyBoy12       | 
adamApple        | 12

Using my server side language this is easily fixed, by replacing null values with a zero. But I would like to have the zeros coming straight from SQL so I can order by the counts.

Any suggestions would be marvelous.

Answer 1

Try the IFNULL Function

SELECT mem.member_id, mem.screen_name, mem.firstname, mem.lastname, mem.country_code,  
mem.joined, rep.rep as reputation, IFNULL(com.cnt,0) as comments FROM members AS mem 
LEFT OUTER JOIN ( 
    SELECT member_id, SUM(awarded_what) as rep 
    FROM members_reputation 
    GROUP BY member_id) rep 
    ON mem.member_id = rep.member_id 
LEFT OUTER JOIN ( 
    SELECT member_id, COUNT(comment_id) as cnt 
    FROM blog_comments 
    GROUP BY comment_id) com 
    ON mem.member_id = com.member_id 
GROUP BY mem.member_id 
ORDER BY mem.joined DESC