返回用户没有的ID

Question

I have two database tables. One is egl_achievement and the other is egl_achievement_member. One just holds achievements, and the other holds members who have achievements. I'm trying to write a query that will return all achievements a member doesn't have. I thought I could use MINUS, but mysql doesn't support that.

SELECT egl_achievement.id as id FROM egl_achievement LEFT JOIN egl_achievement_member ON egl_achievement.id = egl_achievement_member.egl_achievement_id WHERE egl_achievement_member.member_id =57;

This will obviously return the ids that member 57 has, but how can I get the opposite?

Answer 1

You can use a subselect which contains all achievments and then just list those which are not contained:

SELECT egl_achievement.id as id
FROM egl_achievement
WHERE egl_achievement.id NOT IN(
    SELECT egl_achievement_member.egl_achievement_id
    FROM egl_achievement_member
    WHERE egl_achievement_member.member_id =57);