New records with common data

Question

I have a table like this (MySQL 5.0.x, MyISAM):

user{id, login, ip, banned} (Banned: 0 false, 1 true)

I would like to find all users not banned (banned=0) if at least 5 other users with the same ip have already been banned (banned=1).

Thanks for your help! :)

Answer 1

If you have lots of banned users:

SELECT  *
FROM    user uo
WHERE   EXISTS (
        SELECT  1
        FROM    user ui
        WHERE   ui.ip = uo.ip
                AND banned = 1
        LIMIT 4, 1
        )
        AND banned = 0

If you have few banned users:

SELECT  *
FROM    user
WHERE   ip IN (
        SELECT  ip
        FROM    user
        WHERE   banned = 1
        GROUP BY
                ip
        HAVING  COUNT(*) >= 5
        )
        AND banned = 0

In both cases, having an index on (ip, banned) will improve these queries a lot.

Answer 2

SELECT id
FROM user
WHERE ip IN (
 SELECT DISTINCT ip
 FROM user
 WHERE COUNT(*) >= 5
  AND banned = 1
 GROUP BY ip
)
 AND banned = 0