Mysql group_concact what am i doing wrong

Question

I am trying to get all favorite users of a particular user using this simple sub-query

select * from users u 
where u.user_id in 
(
    select GROUP_CONCAT(f.favorite_id SEPARATOR ',') as favourites 
    from favourite_user f
    where f.user_id in(14) group by user_id 
) 

When I run the subquery select GROUP_CONCAT(f.favorite_id SEPARATOR ',') as favourites from favourite_user f where f.user_id in(14) group by user_id it gives me result 6,8,11,10,13,15,7,12

and when i run this query select * from users u where u.user_id in (6,8,11,10,13,15,7,12) it is returning 7 rows of result

But when i run the above mentioned main query it is just giving me the 1 row (the first one) instead of 7.

Can anyone explain me what am i doing wrong. I know this can also be done with joins but I'd like to know why this approach isn't working

Thank you in advance

Answer 1

You don't need GROUP_CONCAT() . Try

select * 
  from users
 where user_id in 
(
    select favorite_id 
      from favourite_user
     where user_id = 14
)

Here is SQLFiddle demo