MySQL Query

I have two tables; a and b. The following is the structure for said tables:

a
---------
a_id int
name

b
---------
b_id int
a_id int
b_name

The two tables have a 1 to many relationship; therefore for every one record in table a, there could be many records in table b that are related.

Here is the problem....

I am running the following SQL and getting the following results:

SELECT a.a_id, b.b_id FROM a INNER JOIN b ON a.a_id = b.a_id;

1,1
1,2
1,3
1,4
1,5
1,6
2,1
2,6
3,1
3,4
4,1
5,2

Instead of getting a multiple returned rows for each record in table b, is there a way to get them on a single line so the returned record sets look like this:

1,1,2,3,4,5,6
2,1,6
3,1,4
4,1
5,2