Difference in queries

Question

can someone let me know difference between following queries.. why they return different results for the 4th column.
SELECT      CUSTOMER.BILL_CYCLE,
CUSTOMER.PARTITION_ID,
COUNT(*),
(select count(1)
from Subscriber S , Customer C
where S.customer_id = C.customer_id
and S.sub_status='A'
and C.BILL_CYCLE = Customer.BILL_CYCLE
and C.PARTITION_ID = CUSTOMER.PARTITION_ID)
FROM CUSTOMER
group by BILL_CYCLE, PARTITION_ID
SELECT bill_cycle, partition_id, COUNT (*),SUM (subs_per_customer)
FROM (SELECT /*+ use_hash(c s) parallel(c,4) */
bill_cycle, partition_id, c.customer_id,
COUNT (DECODE (s.subscriber_no, NULL, 0, 1)) subs_per_customer
FROM subscriber s, customer c
WHERE s.customer_id(+) = c.customer_id AND s.sub_status(+) = 'A'
GROUP BY bill_cycle, partition_id, c.customer_id)
GROUP BY bill_cycle, partition_id

Answer 1

Try something like this. And just dont say its slow. Paste the explain plan and the table structure also.
SQL> create table customer(bill_cycle number, partition_id number, customer_id number);
Table created.
SQL> insert into customer values (1,1,1);
1 row created.
SQL> insert into customer values (1,1,2);
1 row created.
SQL> insert into customer values (1,1,3);
1 row created.
SQL> insert into customer values (1,1,4);
1 row created.
SQL> insert into customer values (1,1,5);
1 row created.
SQL> create table subscriber(customer_id number, sub_status char(1));
Table created.
SQL> insert into subscriber values (1,'A');
1 row created.
SQL> insert into subscriber values (2,' ');
1 row created.
SQL> insert into subscriber values (3,'A');
1 row created.
SQL> insert into subscriber values (4,' ');
1 row created.
SQL> insert into subscriber values (5,'A');
1 row created.
SQL> commit
  2  /
Commit complete.
SQL>  SELECT bill_cycle,
  2     partition_id,
  3     count(*) cnt,
  4     sum(cnt) sm
  5     FROM (SELECT c.bill_cycle,
  6             c.partition_id,
  7             (SELECT count(1)
  8                FROM subscriber s
  9               WHERE s.customer_id  = c.customer_id
10                 AND s.sub_status   = 'A') cnt
11        FROM customer c)
12    GROUP BY bill_cycle,
13     partition_id
14  /
BILL_CYCLE PARTITION_ID        CNT         SM
         1            1          5          3Edited by: Karthick_Arp on Oct 15, 2008 11:59 PM
Corrected the typo