MySQL: refind groups of user from group description - mysql

Question

I have a problem to find the group membership for users. (yes it's not very clear like that)
For example:
I have 2 table:
- one contains a user list with their permission:
userId | permission
-------|-----------
1 | build
1 | play
1 | jump
2 | build
2 | jump
2 | run
3 | drink
3 | build
4 | run
-the second table contain the group and him permisson:
groupId | permission
--------|-----------
G1 | build
G1 | jump
G2 | play
G2 | jump
G3 | drink
G3 | run
G4 | drink
G5 | build
My goal is to find all the groups that the user can have:
userId | groupId
-------|-----------
1 | G1
1 | G2
1 | G5
2 | G1
2 | G5
3 | G4
3 | G5
I have created a request to find which users belong to the group but I can not do this for all my groups (I have more than 1000 group in my datasets):
SELECT DISTINCT userId
FROM (
SELECT userId, count(*) AS nbData
from table_a
WHERE permission in (
SELECT permission
from table_b
where groupId = 'g1'
)
group by userId
) as t
where nbData = (SELECT count(*) from table_b where groupId = 'g1');
An user belongs to a group if he has all the permission of the group. And the goal is to find every group of each user

Answer 1

If you don't have duplicates in either table, you can join the tables together on permissions and aggregate:
select up.userId, gp.groupId
from user_permissions up join
group_permissions gp
on up.permission = gp.permission
group by up.userId, gp.groupId
having count(*) = (select count(*)
from group_permissions gp2
where gp2.groupId = gp.groupId
);
The user is in the group if all the permissions for the group match.

Answer 2

Something like this might work:
SELECT DISTINCT
a.userId,
b.groupId
FROM
table_a a
JOIN table_b b
ON a.permission = b.permission

Answer 3

E.g.:
DROP TABLE IF EXISTS user_permissions;
CREATE TABLE user_permissions
(user_id INT NOT NULL
,permission VARCHAR(12) NOT NULL
,PRIMARY KEY(user_id,permission)
);
INSERT INTO user_permissions VALUES
(1,'build'),
(1,'play'),
(1,'jump'),
(2,'build'),
(2,'jump'),
(2,'run'),
(3,'drink'),
(3,'build'),
(4,'run');
DROP TABLE IF EXISTS group_permissions;
CREATE TABLE group_permissions
(group_id INT NOT NULL
,permission VARCHAR(12) NOT NULL
,PRIMARY KEY(group_id,permission)
);
INSERT INTO group_permissions VALUES
(101,'build'),
(101,'jump'),
(102,'play'),
(102,'jump'),
(103,'drink'),
(103,'run'),
(104,'drink'),
(105,'build');
SELECT DISTINCT u.user_id
, g.group_id
FROM user_permissions u
JOIN group_permissions g
ON g.permission = u.permission -- groups that users potentially belong to
LEFT
JOIN
( SELECT DISTINCT x.user_id
, y.group_id
FROM user_permissions x
LEFT
JOIN group_permissions y
ON y.permission = x.permission
LEFT
JOIN group_permissions z
ON z.group_id = y.group_id
LEFT
JOIN user_permissions a
ON a.user_id = x.user_id
AND a.permission = z.permission
WHERE a.user_id IS NULL
) n -- groups that users don't belong to (this could be much simpler ;-) )
ON n.user_id = u.user_id
AND n.group_id = g.group_id
WHERE n.user_id IS NULL;
+---------+----------+
| user_id | group_id |
+---------+----------+
| 1 | 101 |
| 1 | 105 |
| 1 | 102 |
| 2 | 101 |
| 2 | 105 |
| 3 | 105 |
| 3 | 104 |
+---------+----------+