Question

so I’m having trouble selecting a field only if another fields value is not equal to 0.

So, here’s what’s going on.

I have 3 tables, they are – users, schools, campuses

And basically, I need to select a single users data from these 3 tables. I’d like to only select the campus_name field from campuses if the users.campus_id field is not 0.

So, something pseudo coded like this might give you a better idea..

The query is being passed in a $id variable, that has some user’s id.

SELECT users.*, schools.*, (if(users.campus_id != 0) then campuses.campus_name) 
FROM users, schools, campuses 
WHERE users.id = '$id' (if(users.campus_id != 0) then AND campuses.id = users.campus_id)

Answer 1

SELECT *
FROM schools, 
    users LEFT OUTER JOIN campuses 
        ON users.campus_id != 0 
        AND users.campus_id = campuses.id
WHERE users.school_id = schools.id