select distinct records after performing join

[phpgurullc]

i have two tables a,b,..with approximately 2lac records in each,..

table a
--------------------
a_id a_title

5 abc

6 xyz

table b
---------------------------
b_id a_id

123 5
123 6



i want all the records from table a having distinct a_title which matches with table b,the query i am trying is

select b.b_id, a.a_title,GROUP _CONCAT(a.id) as id from a inner join b on a.a_id=b.b_id where b.b_id=123 group by a.a_title

the above query is taking lots of time,kindly suggest an optimized way for this.

[dgreenhouse]

I'm unclear on why you're using the group_concat...

Maybe this will help:

select b.id,a.title from tablea a
join tableb b on b.id = a.id
where b.id=123
group by a.title order by b.id