Insert, update and delete on updatable join views

Question

Hi I need to insert, update and delete data in a views. I tried the foloing example
http://download-uk.oracle.com/docs/cd/B14117_01/server.101/b10739/views.htm#i1006232
We have two tables:
CREATE TABLE dept (
deptno NUMBER(4) PRIMARY KEY,
dname VARCHAR2(14),
loc VARCHAR2(13));
CREATE TABLE emp (
empno NUMBER(4) PRIMARY KEY,
ename VARCHAR2(10),
job VARCHAR2(9),
mgr NUMBER(4),
sal NUMBER(7,2),
comm NUMBER(7,2),
deptno NUMBER(2),
FOREIGN KEY (DEPTNO) REFERENCES DEPT(DEPTNO));
and one view:
CREATE VIEW emp_dept AS
SELECT emp.empno, emp.ename, emp.deptno, emp.sal, dept.dname, dept.loc
FROM emp, dept
WHERE emp.deptno = dept.deptno
AND dept.loc IN ('DALLAS', 'NEW YORK', 'BOSTON');
this update command works successfully
UPDATE emp_dept
SET sal = sal * 1.10
WHERE deptno = 10;
but this one fails because it attempts to modify the base dept table, and the dept table is not key preserved in the emp_dept view.:
UPDATE emp_dept
SET loc = 'BOSTON'
WHERE ename = 'SMITH';
I tried to create the view with "WITH CHECK OPTION" clause but whith no success :(
My question is: how can I do this with a simple across this view. I rather not use Instead Of Trigger because it take a lot of PL/SQL code :(
thanks in advance
Operator

Answer 1

UPDATE emp_dept
SET loc = 'BOSTON'
WHERE ename = 'SMITH';But that doesn't make sense. You cannot just LOC for SMITH, because LOC is not an attribute of EMP. If you change the LOC in the view then you must change it for all employees in DEPT 30 (or whatever).
The key preserved thing is merely about maintaining your data integrity.
I rather not use Instead Of Trigger because it take a lot of PL/SQL code :(The problem is, your business rule is not clear. Are you wanting to change the LOC for the DEPT record which is the DEPTNO to which SMITH belongs? Or are you wanting to change SMITH's DEPTNO to be the one for the BOSTON office?
Cheers, APC