Group values by a common value: userid and ipaddress

Question

I\'m working on a problem in my database. I\'m trying to find the users who are using multiple accounts. I have a list of user IDs and used IP addresses, like this:

Us

Answer 1

Taking the data from your example:

+--------+---------+
| userid | address |
+--------+---------+
| 1      | 12      |
| 5      | 12      |
| 1      | 13      |
| 2      | 23      |
| 9      | 23      |
| 2      | 56      |
| 4      | 56      |
+--------+---------+

for a table defined as

CREATE TABLE table_27620030 (
    userid INTEGER,
    address INTEGER
);

the following query will list all userids that share the same address (and the address):

SELECT address, GROUP_CONCAT(userid) userids
  FROM table_27620030
  GROUP BY address
  HAVING COUNT(DISTINCT userid) > 1
  ORDER BY address
;

result:

+---------+---------+
| address | userids |
+---------+---------+
| 12      | 1,5     |
| 23      | 2,9     |
| 56      | 2,4     |
+---------+---------+