SQL: Where NOT IN query - mysql

Question

So in the database, there's a table named roles_users. This holds all the roles that the users have. Here, there's two columns: user_id, role_id.
A normal user, with no extra roles has 1 row in this table. This row has role_id 1.
A admin user, has 2 rows in this table. One with role_id 1, and one row with role_id 2
Like this:
user_id role_id
88 1
88 2
99 1 // Only one row with that user_id, so he's a user
Now im trying to count how many users/admin/sellers/partners that exists.
Sellers have 3 rows, one with role_id 1, role_id 2 and role_id 3.
Partner has role_id 1, role_id 4
So i tried this:
SELECT user_id FROM roles_users WHERE role_id IN (1) // MEMBERS ONLY
SELECT user_id FROM roles_users WHERE role_id IN (1,2) // ADMIN
SELECT user_id FROM roles_users WHERE role_id IN (1,2,3) // SELLER
SELECT user_id FROM roles_users WHERE role_id IN (1,4) // PARTNERS
But these queries does not work properly. They give me a count that is way over than its supposed to be. And i believe this is because that it does not EXCLUDE any rows,
I mean at the query when it should look for role_id 1, for members, it includes partners,admin,sellers too because it only check for if it theres any with the row role_id 1 and thats it.
So how can i do this right? So when it looks after members, it should also make sure that the user_id does not have any more rows with other role_ids like 2,3,4

Answer 1

group_concat is what you want:
select
case roles
when '1' then 'members'
when '1,2' then 'admins'
when '1,2,3' then 'sellers'
when '1,4' then 'partners'
else 'uh??'
end role,
count(user_id) nr_users from (
select user_id, group_concat(role_id order by role_id separator ',') roles
from roles_users
group by user_id
)
group by role
order by role;
And by the way, you could store roles more efficiently using a bitmask. Advantage: only one column per user id. Disadvantage: harder to build queries...

Answer 2

This will give you all combinations of privileges in the table with their count
SELECT
COUNT(*) AS num
GROUP_CONCAT(role_id ORDER BY role_id) AS privilegeset
FROM roles_users
GROUP BY user_id

Answer 3

Concerning sellers and partners:
As I understand it, sellers are the only ones that can have role_id = 3 and partners are the only ones that can have role_id = 4, correct?
If yes, finding sellers and partners is quite easy:
SELECT user_id FROM roles_users WHERE role_id = 3 // SELLER
SELECT user_id FROM roles_users WHERE role_id = 4 // PARTNERS

Answer 4

Not the most elegant, but a start
SELECT user_id
,CASE WHEN (role1 > 0 AND 0 = role2 AND 0 = role3 AND 0 = role4) THEN 'MEMBER'
WHEN (role1 > 0 AND role2 > 0 AND 0 = role3 AND 0 = role4) THEN 'ADMIN'
WHEN (role1 > 0 AND role2 > 0 AND role3 > 0 AND 0 = role4) THEN 'SELLER'
WHEN (role1 > 0 AND 0 = role2 AND 0 = role3 AND role4 > 0) THEN 'PARTNER'
ELSE 'Something else'
END AS type
FROM (
SELECT user_id
,SUM( CASE role_id WHEN 1 THEN 1 ELSE 0 END) AS role1
,SUM( CASE role_id WHEN 2 THEN 1 ELSE 0 END) AS role2
,SUM( CASE role_id WHEN 3 THEN 1 ELSE 0 END) AS role3
,SUM( CASE role_id WHEN 4 THEN 1 ELSE 0 END) AS role4
FROM roles_users
GROUP BY user_id
) x
EDIT: I guess this is answering the wrong question, it is showing the type of each user.

Answer 5

Here's a solution using INTERSECT and MINUS. Sadly these are not supported by MySQL yet but maybe someone will find this useful nonetheless.
-- Find users with Role 1
SELECT user_id FROM
(SELECT user_id, role_id FROM roles_users WHERE role_id = 1)
MINUS SELECT user_id FROM roles_users WHERE role_id NOT IN (1)
-- Find users with Roles 1 and 2
SELECT user_id FROM
(SELECT user_id, role_id FROM roles_users WHERE role_id = 1
INTERSECT SELECT user_id, role_id FROM roles_users WHERE role_id = 2)
MINUS SELECT user_id FROM roles_users WHERE role_id NOT IN (1,2)
-- Find users with Roles 1, 2, 3
SELECT user_id FROM
(SELECT user_id, role_id FROM roles_users WHERE role_id = 1
INTERSECT SELECT user_id, role_id FROM roles_users WHERE role_id = 2
INTERSECT SELECT user_id, role_id FROM roles_users WHERE role_id = 3)
MINUS SELECT user_id FROM roles_users WHERE role_id NOT IN (1,2,3)
-- Find users with Roles 1, 4
SELECT user_id FROM
(SELECT user_id, role_id FROM roles_users WHERE role_id = 1
INTERSECT SELECT user_id, role_id FROM roles_users WHERE role_id = 4)
MINUS SELECT user_id FROM roles_users WHERE role_id NOT IN (1,4)

Answer 6

Here's a join-based solution that hopefully works on any SQL.
SELECT user_id FROM roles_users RU0
LEFT JOIN roles_users RU1 ON RU0.user_id = RU1.user_id AND RU1.role_id = 1
LEFT JOIN roles_users RU2 ON RU0.user_id = RU2.user_id AND RU2.role_id = 2
LEFT JOIN roles_users RU3 ON RU0.user_id = RU3.user_id AND RU3.role_id = 3
LEFT JOIN roles_users RU4 ON RU0.user_id = RU4.user_id AND RU4.role_id = 4
WHERE RU1.user_id IS NOT NULL -- should have role 1
AND RU2.user_id IS NULL -- should NOT have role 2
AND RU3.user_id IS NULL -- should NOT have role 3
AND RU4.user_id IS NOT NULL -- should have role 4
Just vary the "IS NULL" and "IS NOT NULL" in the where clause to change which roles you want the user to have or not have.