How to filter SQL results in a has-many-through relation

Question

Assuming I have the tables student, club, and student_club:

student {
    id
    name
}
club {
    id
    name
}
stude         


        

Answer 1

SELECT *
FROM   student
WHERE  id IN (SELECT student_id
              FROM   student_club
              WHERE  club_id = 30
              INTERSECT
              SELECT student_id
              FROM   student_club
              WHERE  club_id = 50)  

Or a more general solution easier to extend to n clubs and that avoids INTERSECT (not available in MySQL) and IN (as performance of this sucks in MySQL)

SELECT s.id,
       s.name
FROM   student s
       join student_club sc
         ON s.id = sc.student_id
WHERE  sc.club_id IN ( 30, 50 )
GROUP  BY s.id,
          s.name
HAVING COUNT(DISTINCT sc.club_id) = 2