I want to find items in common from the "following_list" column in a table of users: +----+--------------------+-------------------------------------+ | id | name | following_list | +----+--------------------+-------------------------------------+ | 9 | User 1 | 26,6,12,10,21,24,19,16 | | 10 | User 2 | 21,24 | | 12 | User 3 | 9,20,21,26,30 | | 16 | User 4 | 6,52,9,10 | | 19 | User 5 | 9,10,6,24 | | 21 | User 6 | 9,10,6,12 | | 24 | User 7 | 9,10,6 | | 46 | User 8 | 45 | | 52 | User 9 | 10,12,16,21,19,20,18,17,23,25,24,22 | +----+--------------------+-------------------------------------+ I was hoping to be able to sort by the number of matches for a given user id. For example, I want to match all users except #9 against #9 to see which of the IDs in the "following_list" column they have in common. I found a way of doing this through the "SET" datatype and some bit trickery: http://dev.mysql.com/tech-resources/articles/mysql-set-datatype.html#bits However, I need to do this on an arbitrary list of IDs. I was hoping this could be done entirely through the database, but this is a little out of my league. Any bit gurus out there? Thanks, Landon