Outer Join doesnt work Y?

Question

Hi All,
Can anybody explain me, Y this outerjoin is not working.
Table TERMINAL_MASTER has got terminal_i, terminal_name 25 terminals are there.
DAY_BOOK table has got terminal_id,amount column is there. everyday it is not all the terminals sends money.
i want to see the result like this all terminals, and who ever sends money i want see the amount, who ever not sends money, i want to see 0 (zero) figure. but im not getting all terminals list, im getting only list of terminals only in daybook table.
select A.terminal_name,SUM(B.amount) from terminal_master A,day_book b
where A.terminal_id = B.terminal_id (+)
and
B.transaction_date = '1-mar-05'
group by
A.terminal_name
Thanks in advance.

Answer 1

The reason is that one part of your where condition:
A.terminal_id = B.terminal_id (+) says that matching row in B may or may not be present. If not present, assume the columns coming from table B as having NULL value. while the other part of your where condition:
B.transaction_date = '1-mar-05' says that column transaction_date coming from table B must match the value '1-mar-05'. So, in case when matching row in B is not found, it will assume that columns from B are having a value NULL which cannot satisfy your B.transaction_date condition. That is why you need to tell the system to ignore that condition too (in cases where a matching row in B is not found).
Also, as pointed out earlier, if transaction_date is really a DATE type column, the value that it is compared to ('1-mar-05') must also be of DATE type (use TO_DATE with format to avoid surprises).