Question

Is it possible to convert the following subquery to a JOIN, preferably without a derived table?

SELECT * FROM users u
LEFT JOIN user_groups ug ON u.usergroupid=ug.groupid
WHERE
u.userstatus=1 AND
ug.groupstatus=1 AND
ug.grouprank>=(SELECT grouprank FROM user_groups WHERE groupkey='users')

The user_groups table looks like:

+-------------+---------------------+------+-----+---------+----------------+
| Field       | Type                | Null | Key | Default | Extra          |
+-------------+---------------------+------+-----+---------+----------------+
| groupid     | tinyint(3) unsigned | NO   | PRI | NULL    | auto_increment |
| groupkey    | varchar(8)          | NO   |     | NULL    |                |
| grouprank   | smallint(6)         | NO   |     | NULL    |                |
| groupstatus | tinyint(1) unsigned | NO   |     | NULL    |                |
+-------------+---------------------+------+-----+---------+----------------+

The users table looks like:

+--------------+---------------------+------+-----+---------+----------------+
| Field        | Type                | Null | Key | Default | Extra          |
+--------------+---------------------+------+-----+---------+----------------+
| userid       | int(10) unsigned    | NO   | PRI | NULL    | auto_increment |
| username     | varchar(32)         | NO   |     | NULL    |                |
| userpassword | varchar(32)         | NO   |     | NULL    |                |
| usergroupid  | tinyint(3) unsigned | NO   |     | NULL    |                |
| userstatus   | tinyint(1) unsigned | NO   |     | NULL    |                |
+--------------+---------------------+------+-----+---------+----------------+

Answer 1

I think this is what you’re looking for — give it a test.

SELECT * FROM users u
LEFT JOIN user_groups ug ON u.usergroupid=ug.groupid
JOIN user_groups ug2 ON ug.grouprank >= ug2.grouprank AND ug2.groupkey = 'users'
WHERE
u.userstatus=1 AND
ug.groupstatus=1