Group by making difference in result when only when ID is selected.

Question

The following query returns nothing since there is no data matching criteria in tables which looks good to me:
SELECT SUM (ci.premium_amt),'START PROGRAM'
FROM hr.group cg,
hr.request pi,
hr.rate ri,
hr.info cc,
hr.allocation ci,
hr.index fi
WHERE cg.product_id = 555
AND cg.r_id = 222
AND cg.product_id = pi.product_id
AND cg.r_id = pi.r_id
AND pi.product_id = ri.product_id
AND pi.r_id = ri.r_id
AND cg.group_id = cc.group_id
AND cc.cost_id = ci.cost_id
AND cc.index_id = fi.index_id
group by  cg.product_id;
But when i remove the group by clause in the above query as follows:
SELECT SUM (ci.premium_amt),'START PROGRAM'
FROM hr.group cg,
hr.request pi,
hr.rate ri,
hr.info cc,
hr.allocation ci,
hr.index fi
WHERE cg.product_id = 555
AND cg.r_id = 222
AND cg.product_id = pi.product_id
AND cg.r_id = pi.r_id
AND pi.product_id = ri.product_id
AND pi.r_id = ri.r_id
AND cg.group_id = cc.group_id
AND cc.cost_id = ci.cost_id
AND cc.index_id = fi.index_id
I get output as:
(null) START PROGRAM
I was expecting output as nothing as that id does not exist.
Help is appreciated.

Answer 1

user10857924 wrote:
since there are no rows produce, group by retrun nothing i.e. no rows to group by
where as when you apply aggregate function i.e. min/max etc without group it tends to produce atmost one rows even there is no row return
please look at below example hope this will clarify
with t(id, amt) as
     select 1, 10 from dual union all
     select 1, 10 from dual union all
     select 2, 30 from dual
select sum(amt), 'Total'
from t where id=99
with t(id, amt) as
     select 1, 10 from dual union all
     select 1, 10 from dual union all
     select 2, 30 from dual
select sum(amt), 'Total'
from t where id=99
group by id
Thanks
Edited by: user10857924 on Sep 21, 2010 3:35 PMI am getting the following error:
SQL> with t(id, amt) as
2 (
3 select 1, 10 from dual union all
4 select 1, 10 from dual union all
5 select 2, 30 from dual
6 )
7 select sum(amt), 'Total'
8 from t where id=99;
with t(id, amt) as
ERROR at line 1:
ORA-32033: unsupported column aliasing