Combining rows with comma delimited

Question

Hi All,
I have two tables
Table A
ID Location ID
1 6
2 7
1 9
2 10
3 7
1 8
2 9
Table B
ID
1
2
3
49
8
6
I have to come up with something like this for each ID in table B, I have to write a query to get
ID Location ID
1 6, 9, 8
2 7, 10, 9
so for each Id I need to grab there Location Id and concatenate them with comma.
How can I acheive this. Is it possible to avoid loops in this case?
Anye help will be apprecaited.

Answer 1

with a as (
           select 1 id,6 location_id from dual union all
           select 2,7 from dual union all
           select 1,9 from dual union all
           select 2,10 from dual union all
           select 3,7 from dual union all
           select 1,8 from dual union all
           select 2,9 from dual
     b as (
           select 1 id from dual union all
           select 2 from dual union all
           select 3 from dual union all
           select 49 from dual union all
           select 8 from dual union all
           select 6 from dual
-- end of on-the-fly data sample
select  id,
        rtrim(xmlagg(xmlelement(e,location_id,',').extract('//text()') order by rn),',') location_id_list
  from  (
         select  a.id,
                 a.location_id,
                 row_number() over(partition by a.id order by a.location_id) rn
           from  a,
                 b
           where b.id = a.id
  group by id
        ID LOCATION_ID_LIST
         1 6,8,9
         2 7,9,10
         3 7
3 rows selected.
SQL> SY.