improving query or logic in a oracle stored procedure? - stored-procedures

Question

I have 3 tables as follows:
CUSTOMER
CIF SUMOFALLACCOUNTBALACE
A1 6000
A2 2000
A3 7000
ACCOUNT
ACCOUNTNUMBER ACCOUNTBALANCE
B1 1000
B2 2000
B3 3000
B4 4000
B5 5000
RELATION
CIF ACCOUNTNUMBER
A1 B1
A1 B5
A2 B2
A3 B3
A3 B4
I need to update SUMOFALLACCOUNTBALACE in CUSTOMER table of all the available ACCOUNTNUMBERs of respective CIFs using RELATION table.
The sample query I built for 1 by 1 CIF is :-
UPDATE CUSTOMER
SET SUMOFALLACCOUNTBALACE =
(SELECT SUM(ACCOUNTBALANCE)
FROM ACCOUNT
WHERE ACCOUNTNUMBER IN
(SELECT ACCOUNTNUMBER
FROM RELATION
WHERE CIF IN
(SELECT CIF
FROM CUSTOMER
WHERE CIF = 'A1')))
WHERE CIF = 'A1'
which is giving me right results but it is taking time when large data, also I need to pass CIF 1 by 1 in oracle procedure using loop.
Can anybody please suggest a better way to do this?
Thanks in Advance,
Gopal Arora

Answer 1

You could execute a single statement which updates all SUMOFACCOUNTBALANCEs in one go:
UPDATE CUSTOMER C
SET SUMOFALLACCOUNTBALACE =
(SELECT SUM(A.ACCOUNTBALANCE)
FROM RELATION R
INNER JOIN ACCOUNT A
ON (A.ACCOUNTNUMBER = R.ACCOUNTNUMBER)
WHERE R.CIF = C.CIF)
However, in general, you should not store the results of computations due to the danger of the computation result not being kept up to date when the elements forming that computation are changed. It would be better if you did not have a CUSTOMER.SUMOFALLACCOUNTBALACE column and instead you calculated it from the base data when required. In this way you can be assured that its value is correct at all times.
SELECT C.CIF
,SUM(A.ACCOUNTBALANCE) SUMOFALLACCOUNTBALACE
FROM CUSTOMER C
LEFT OUTER JOIN RELATION R
ON (R.CIF = C.CIF)
LEFT OUTER JOIN ACCOUNT A
ON (A.ACCOUNTNUMBER = R.ACCOUNTNUMBER)