Get permissions for a given user

Question

I wrote a large MySQL query to retrieve all permissions for a given user, and recently found that this does not work in newer versions of MySQL due to the ONLY_FULL_GROUP_BY mode.

The query to retrieve all granted permissions for a given user is:

SELECT
    `name`,
    `display_name`,
    `description`
FROM(
    SELECT * FROM (
        SELECT
            `p`.`id`,
            `p`.`name`,
            `p`.`display_name`,
            `p`.`description`,
            MAX(`r`.`priority`),
            IFNULL(`up`.`is_granted`, `rp`.`is_granted`) AS `is_granted`
        FROM `permissions` AS `p`
        LEFT JOIN `user_permissions` AS `up`
            ON `up`.`permission` = `p`.`id`
            AND `up`.`user` = 1
        LEFT JOIN `role_permissions` `rp`
            ON `rp`.`permission` = `p`.`id`
            AND `rp`.`role` IN(
                SELECT
                    `ur`.`role`
                FROM `user_roles` AS `ur`
                WHERE `ur`.`user` = 1
            )
        LEFT JOIN `roles` AS `r`
            ON `r`.`id` = `rp`.`role`
        GROUP BY `r`.`priority` DESC, `rp`.`permission`, `up`.`permission`
    ) AS `res`
    GROUP BY `res`.`id` ASC
) AS `res`
WHERE `res`.`is_granted` = 1

This produces the following error on newer MySQL installations with the flag ONLY_FULL_GROUP_BY enabled (it is enabled by default): SQL Error (1055): Expression #5 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'res.MAX(r.priority)' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by.

I tried to completely re-wrote the query to be more efficient and work with the flag enabled, however it does not quite achieve the same goal as the first query.

SELECT
    u.id AS user_id,
    u.email AS user_email,
    up.permission AS user_permission_id,
    up.is_granted AS user_permission_is_granted,
    upp.name AS user_permission_name,
    upp.display_name AS user_permission_display_name,
    upp.description AS user_permission_description,
    ur.role AS role_id,
    urr.name AS role_name,
    urr.display_name AS role_display_name,
    urr.priority AS role_priority,
    urp.permission AS role_permission_id,
    urp.is_granted AS role_permission_is_granted,
    urpp.name AS role_permission_name,
    urpp.display_name AS role_permission_display_name,
    urpp.description AS role_permission_description
FROM users u
LEFT JOIN user_permissions up
    ON up.user = u.id
LEFT JOIN permissions upp
    ON upp.id = up.permission
LEFT JOIN user_roles ur
    ON ur.user = u.id
LEFT JOIN roles urr
    ON urr.id = ur.role
LEFT JOIN role_permissions urp
    ON urp.role = ur.role
LEFT JOIN permissions urpp
    ON urpp.id = urp.permission
WHERE u.id = 1

How should I do this? I have given it a couple tries and cannot really see a way to only return rows with the highest priority without disabling the ONLY_FULL_GROUP_BY mode.

Should I resort to just using the newer query and applying the role priority in application code rather than in the SQL query?

Here is a DBFiddle with database structure and query.

Given the data from the DBFiddle above, I want the result set to look like the following:

| user_id | user_email        | permission_id | permission_name | permission_display_name | permission_description                             | is_granted |
| ------- | ----------------- | ------------- | --------------- | ----------------------- | -------------------------------------------------- | ---------- |
| 1       | user1@example.com | 1             | test1           | Test permission 1       | Role permission, should ONLY be granted to user 1  | 1          |
| 1       | user1@example.com | 2             | test2           | Test permission 2       | Role permission, should ONLY be granted to user 1  | 1          |
| 1       | user1@example.com | 3             | test3           | Test permission 3       | Role permission, should ONLY be granted to user 2  | 0          |
| 2       | user2@example.com | 3             | test3           | Test permission 3       | Role permission, should ONLY be granted to user 2  | 1          |
| 1       | user1@example.com | 4             | test4           | Test permission 4       | Role permission, should be granted to user 1 and 2 | 1          |
| 2       | user2@example.com | 4             | test4           | Test permission 4       | Role permission, should be granted to user 1 and 2 | 1          |
| 1       | user1@example.com | 5             | test5           | Test permission 5       | User permission, granted to user 1                 | 1          |
| 2       | user2@example.com | 6             | test6           | Test permission 6       | User permission, granted to user 2                 | 1          |

The reason I want permission ID 3 to return is_granted = 0 instead of not appearing in the result set is because the user is initially granted the permission, but then not granted it from role ID 2, which has a higher priority.

This question is not a duplicate of SQL select only rows with max value on a column because it specifically pertains to how I should modify my query to work around the ONLY_FULL_GROUP_BY mode.

user_1928751 · Answer

Solved by looking a bit closer at the duplicate question and understanding how exactly the answers on that question works.

I had to create a view to join together the role_permissions table with the priority column from the roles table. Then I had to get all the highest priority role permissions for each user. Lastly I had to get all the user permissions which are not overriding any role permissions for the user and join this together with the role permissions using a UNION.

Here is my solution:

SELECT
    u.id AS user_id,
    u.email AS user_email,
    p.id AS permission_id,
    p.name AS permission_name,
    p.display_name AS permission_display_name,
    p.description AS permission_description,
    IFNULL(up.is_granted, IFNULL(rp2.is_granted, rp1.is_granted)) AS is_granted
FROM users u
LEFT JOIN role_permissions_withpriority rp1
    ON rp1.role IN(SELECT role FROM user_roles WHERE user = u.id)
LEFT OUTER JOIN role_permissions_withpriority rp2
    ON rp2.role IN(SELECT role FROM user_roles WHERE user = u.id) AND rp2.permission = rp1.permission AND rp2.priority > rp1.priority
LEFT OUTER JOIN user_permissions up
    ON up.user = u.id AND up.permission = rp1.permission
LEFT JOIN permissions p
    ON p.id = rp1.permission
GROUP BY user_id, permission_id, is_granted
UNION
SELECT
    u.id AS user_id,
    u.email AS user_email,
    p.id AS permission_id,
    p.name AS permission_name,
    p.display_name AS permission_display_name,
    p.description AS permission_description,
    up.is_granted AS is_granted
FROM users u
LEFT JOIN user_permissions up
    ON up.user = u.id
LEFT JOIN permissions p
    ON p.id = up.permission
WHERE p.id IS NOT NULL
GROUP BY user_id, permission_id, is_granted

Here is an updated DBFiddle which demonstrates that the solution is working.

Get permissions for a given user

1 Answers