How to get unique values in a string in my sql

Question

For example:

select GROUP_CONCAT(seatnum) 
  from busses 
 where bus_id=19229; 

This is resulting as 7,1,2,3,1,7,4. I have to get only 7,1,2,3,4, i.e unique values in mysql query. Distinct will not solve my problem here.

So pls let me know is their any other ideas in this? Thanks.