Using Aggregate function in queries

Question

Hi all,
          Please take a look on this query and suggest me why i'm getting the error..
This is my simple query using aggregate function in it..
SELECT T1.NAME, T1.DESCRIPTION, SUM(T2.QUANTITY)
FROM TABLE1 T1, TABLE2 T2
WHERE T1.ID=T2.ID
GROUP BY T1.NAME, T1.DESCRIPTION
Above query added with a sub-query in the select segment..
SELECT T1.NAME, T1.DESCRIPTION, SUM(T2.QUANTITY), (SELECT AVG(T3.PRICE) FROM TABLE1 TT1, TABLE3 T3 WHERE TT1.ID=T3.ID AND TT1.ID=T1.ID) AV_PRICE
FROM TABLE1 T1, TABLE2 T2
WHERE T1.ID=T2.ID
GROUP BY T1.NAME, T1.DESCRIPTION
When i add a sub-query which has aggregate function in it, i'm getting the 'ORA-00979: not a GROUP BY expression' error.

Answer 1

What is your DB Version. Your query works without any issue in my DB. I used WITH clause to create the sample data. The query highlighted in BLUE is the actual query.
SQL> select * from v$version where rownum = 1;
BANNER
Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bi
SQL> with table1
  2  as
  3  (
  4    select 1 id, 'karthick' name, 'user name' description from dual
  5  ),
  6  table2
  7  as
  8  (
  9    select 1 id, 100 quantity from dual
10  ),
11  table3
12  as
13  (
14    select 1 id, 10 price from dual
15  )
16  select t1.name
17       , t1.description
18       , sum(t2.quantity)
19       , (
20           select avg(t3.price)
21             from table1 tt1
22                , table3 t3
23            where tt1.id = t3.id
24              and tt1.id = t1.id
25         ) av_price
26    from table1 t1
27       , table2 t2
28   where t1.id = t2.id
29   group
30      by t1.name
31       , t1.description;
NAME     DESCRIPTI SUM(T2.QUANTITY)   AV_PRICE
karthick user name              100         10
SQL>