Question

Given a join table for m-2-m relationship between booth and user

+-----------+------------------+
| booth_id  |          user_id |
+-----------+------------------+
|         1 |                1 |
|         1 |                2 |
|         1 |                5 |
|         1 |                9 |
|         2 |                1 |
|         2 |                2 |
|         2 |                5 |
|         2 |               10 |
|         3 |                1 |
|         3 |                2 |
|         3 |                3 |
|         3 |                4 |
|         3 |                6 |
|         3 |               11 |
+-----------+------------------+

How can I get a distinct set of booth records that are common between a subset of user ids? For example, if I am given user_id values of 1,2,3, I expect the result set to include only booth with id 3 since it is the only common booth in the join table above between all user_id‘s provided.

I’m hoping I’m missing a keyword in MySQL to accompish this. The furthest I’ve come so far is using ... user_id = all (1,2,3) but this is always returning an empty result set (I believe I understand why it is though).

Answer 1

The SQL query for this will be:

select booth_id from table1 where [user_id]
in (1,2,3) group by booth_id having count(booth_id) = 
(select count(distinct([user_id])) from table1 where [user_id] in (1,2,3))

If this could help you creating the MySQL query.