Question

i got this tabels

Users:

id name
1 | tom
2 | jim
3 | bob

User_Has_Toys

user_id toy_id
1      | 2
1      | 3
1      | 4
2      | 2
2      | 4
3      | 4

Toy

id name
1 | toy1
2 | toy2
3 | toy3
4 | toy4
5 | toy5

and i make query

SELECT u.id FROM Users u
LEFT JOIN User_Has_Toys uht ON (u.id = uht.user_id)
LEFT JOIN Toy t ON t.id = uht.toy_id
WHERE t.id IN ('2', '4')

and i get all users
but i need only users with id 1 and 2

could some one help me?

Answer 1

One method to check if a user has multiple specific rows in another table is to filter for those rows and see if count is correct. So for instance, if we count the number of rows in User_Has_Toys for a specific user id and filtering for toys 2 and 4, we should get a count of 2 if and only if the user has both toys 2 and 4 (NOTE: assuming duplicate toy entries are not allowed). The query would look something like this:

 SELECT 
     u.id
 FROM Users AS u
    WHERE 2 = (
        SELECT COUNT(*) FROM User_Has_Toys uht
        WHERE uht.toy_id IN (2,4)
        AND uht.user_id = u.id);

Demo: http://sqlize.com/6yU3OlU2pD

You could also get the same result with a minor modification to your original query by grouping by the user id and checking that the toy count is exactly 2:

SELECT u.id FROM Users u
LEFT JOIN User_Has_Toys uht ON (u.id = uht.user_id)
LEFT JOIN Toy t ON t.id = uht.toy_id
WHERE t.id IN ('2', '4')
group by u.id having count(t.id) = 2;

Demo: http://sqlize.com/7nTYZbJKsn