Question

I have a script to count a users points in a simple achievements type script, then display them on a web page in order. I have the following mySQL function, but if a user doesn’t have any points as yet (i.e there is no ‘pa.userid’ to be found, then the user does not get fetched at all)

SELECT u.userid,
SUM(IF(pa.plus = '1', pa.points_amount, 0)) - SUM(IF(pa.plus = '0', pa.points_amount, 0)) AS points
FROM awarded_points pa,
users u WHERE u.userid = pa.userid 
GROUP BY u.userid 
ORDER BY points DESC 
LIMIT 10

How would i go about making the above code include users that haven’t yet got any points? Is it a complicated change?

Answer 1

Use a left outer join

SELECT u.userid,
       SUM(IF(pa.plus = '1', pa.points_amount, 0)) - SUM(IF(pa.plus = '0', pa.points_amount, 0)) AS points
FROM users u
LEFT OUTER JOIN awarded_points pa ON u.userid = pa.userid 
GROUP BY u.userid 
ORDER BY points DESC 
LIMIT 10

See that great explanation of joins