Updating a column of cursor then using that value to select - oracle

Question

I have a cursor that queries a table like this
CURSOR Cur IS
SELECT Emp_No,status
from Employee
FOR UPDATE OF status;
Now I would want to update my status in Employee table from another table using the Emp_no. Once I have done this I need to use this status for calling custom business logic and not the original status retrieved by the cursor. What is the best way of going about this? Here is what I have written. I declared a variable called v_status by the way
FOR Rec IN Cur LOOP
BEGIN
UPDATE Employee
SET status = (select a.status from Employee_Status where a.Emp_No = rec.Emp_No)
WHERE CURRENT OF Cur ;
COMMIT;
END;
SELECT status INTO v_status
FROM Employee
where Emp_No = rec.Emp_No;
IF(v_status = 'Active') THEN
-- Custom Business Logic
ELSE
-- Business logic
END IF;
END LOOP;
What would be a better way to achieve this?

Answer 1

1) I'm hoping in your real code that you don't have a COMMIT in the middle of your loop. Since committing releases the locks held by your transaction, the row-level locks taken out with the FOR UPDATE clause are released and other sessions are free to update the same rows. In later versions of Oracle, you'll get an "ORA-01002: fetch out of sequence" if you do this. In earlier versions of Oracle, this error was ignored which lead to occasionally incorrect results.
2) Do you need to update the EMPLOYEE table on a row-by-row basis? I'd tend to move the update outside of the loop in order to maximize SQL since that's the most efficient way to process data. If your business logic is amenable to it, I'd also suggest doing bulk operations to fetch the data into local collections that your business logic can iterate through in order to minimize context shifts between SQL and PL/SQL.
So, based on your comments, in your example, there should be a predicate in the definition of your cursor, right? Something like this?
CURSOR Cur IS
SELECT Emp_No,status
from Employee
WHERE status IS NULL
FOR UPDATE OF status;
If so, you'd need that same predicate in the single UPDATE statement (potentially instead of the EXISTS clause). But since you know that you only want to process the rows that your UPDATE statement affected, you can just return those rows into a local collection
DECLARE
CURSOR cur IS
SELECT emp_no, status
FROM employee
WHERE status IS NULL;
TYPE l_employee_array IS
TABLE OF cur%rowtype;
l_modified_employees l_employee_array;
BEGIN
UPDATE employee e
SET status = (select es.status
from employee_status es
where es.emp_no = e.emp_no)
WHERE status IS NULL
AND EXISTS (SELECT 1
FROM employee_status es
WHERE es.emp_no = e.emp_no)
RETURNING emp_no, status
BULK COLLECT INTO l_modified_employees;
FOR i IN l_modified_employees.FIRST .. l_modified_employees.LAST
LOOP
IF( l_modified_employees(i).status = 'Active' )
THEN
-- Custom logic 1
ELSE
-- Custom logic 2
END IF;
END LOOP;
END;

Answer 2

Why not just simply:
FOR Rec IN Cur LOOP
SELECT a.status INTO v_status from Employee_Status a where a.Emp_No = rec.Emp_No;
UPDATE Employee
SET status = v_status
WHERE CURRENT OF Cur ;
COMMIT;
IF(v_status = 'Active') THEN
-- Custom Business Logic
ELSE
-- Business logic
END IF;
END LOOP;

Answer 3

You could use the RETURNING clause:
UPDATE employee
SET status = (SELECT a.status ...)
WHERE CURRENT OF Cur
RETURNING status INTO v_status;