MySQL: what is the most efficient way to retrieve all permissions from RBAC database?

Question

Good day.

I have a role-based access control database and looking for an efficient way to get all permissions user has. This is the schematics:

Now I need to get all user's permission in the most (possibly) efficient way. Tried this query:

SELECT p.name
  FROM permission p
  WHERE p.id = (
    SELECT rpl.permission_id
    FROM role_permission_list rpl
    WHERE rpl.role_id = (
      SELECT url.role_id
      FROM user_role_list url
      WHERE url.user_id = 2
    )
)

But this fails. Since sub-query returns more than 1 result. Tried to think of a join — couldn't figure it out.

Thanks in advance.

PS: In future there will be an permission_overrides table, since one standalone access-controlled entity may have exclusive set of permissions.

Answer 1

Give this a try:

SELECT u.id, p.name
FROM `user` u
LEFT JOIN user_role_list url ON u.id = url.user_id
LEFT JOIN role r ON r.ID = url.role_id
LEFT JOIN role_permission_list rpl ON rpl.role_id = r.id
LEFT JOIN permission p ON p.ID = rpl.permission_id
WHERE u.id = A_Users_ID

Answer 2

It will be simple 3 joins, like:

SELECT
  `user`.id,
  permission.*
FROM
  `user`
    LEFT JOIN user_role_list ON `user`.id=user_role_list.user_id
    LEFT JOIN role_permission_list ON user_role_list.role_id=role_permission_list.role_id
    LEFT JOIN permission ON role_permission_list.permission_id=permission.id
WHERE
  `user`.id=$user_id

(since you're not looking for role description from which specific permission came, I've not include that table to query)