PL/SQL procedure to assign grades to the employees - oracle

Question

create or replace procedure p2
as
CURSOR c1 IS
SELECT salary
FROM employee1
FOR UPDATE;
BEGIN
FOR employee_rec IN c1 LOOP
exit when c1%notfound;
if salary>20000 then
update employee1 set grade='A' WHERE CURRENT OF c1;
if salary>15000 then
update employee1 set grade='B' WHERE CURRENT OF c1;
if salary>10000 then
update employee1 set grade='C' WHERE CURRENT OF c1;
if salary<10000 then
update employee1 set grade='D' WHERE CURRENT OF c1;
end if;
end if;
end if;
end if;
END LOOP;
END p2;
An error shows up as salary is undeclared How can I make this code better to get the desired output???

Answer 1

Why not simply like this:
update employee1 set grade=
case
when salary>20000 then 'A'
when salary>15000 then 'B'
when salary>10000 then 'C'
when salary<10000 then 'D'
ELSE grade -- keep existing grade value
end;

Answer 2

Your error is because there is no variable salary. You have a cursor called employee_rec which contains a column called salary but you would need to reference that using employee_rec.salary.
If we fix that (and indent your code) then it compiles:
CREATE PROCEDURE p2 AS
CURSOR c1 IS
SELECT salary
FROM employee1
FOR UPDATE;
BEGIN
FOR employee_rec IN c1 LOOP
EXIT WHEN c1%NOTFOUND;
IF employee_rec.salary>20000 THEN
update employee1 set grade='A' WHERE CURRENT OF c1;
IF employee_rec.salary>15000 THEN
update employee1 set grade='B' WHERE CURRENT OF c1;
IF employee_rec.salary>10000 THEN
update employee1 set grade='C' WHERE CURRENT OF c1;
IF employee_rec.salary<10000 THEN
update employee1 set grade='D' WHERE CURRENT OF c1;
END IF;
END IF;
END IF;
END IF;
END LOOP;
END p2;
/
However, it isn't going to give you the output you want due to the nested IF statements. If you replace the nested IF statements with ELSIF:
CREATE OR REPLACE PROCEDURE p2 AS
CURSOR c1 IS
SELECT salary
FROM employee1
FOR UPDATE;
BEGIN
FOR employee_rec IN c1 LOOP
EXIT WHEN c1%NOTFOUND;
IF employee_rec.salary>20000 THEN
update employee1 set grade='A' WHERE CURRENT OF c1;
ELSIF employee_rec.salary>15000 THEN
update employee1 set grade='B' WHERE CURRENT OF c1;
ELSIF employee_rec.salary>10000 THEN
update employee1 set grade='C' WHERE CURRENT OF c1;
ELSIF employee_rec.salary<10000 THEN
update employee1 set grade='D' WHERE CURRENT OF c1;
END IF;
END LOOP;
END p2;
/
Then your procedure works (except when the salary is 10,000).
However, you could still make it more efficient by getting rid of the cursor:
CREATE OR REPLACE PROCEDURE p2 AS
BEGIN
UPDATE employee1
SET grade = CASE
WHEN salary > 20000 THEN 'A'
WHEN salary > 15000 THEN 'B'
WHEN salary > 10000 THEN 'C'
ELSE 'D'
END;
END p2;
/
db<>fiddle

Answer 3

It is not
if salary>20000 then
but
if employee_rec.salary>20000 then
Code you wrote can be simplified - up to a single UPDATE statement. However, if you're using PL/SQL for learning, CASE is probably a better option than nested IFs. Something like this example based on subset of Scott's EMP table.
Test data:
SQL> create table test as
2 select empno, ename, sal, 'x' grade
3 from emp
4 where deptno = 10;
Table created.
SQL> select * from test order by sal desc;
EMPNO ENAME SAL G
---------- ---------- ---------- -
7839 KING 5000 x
7782 CLARK 2450 x
7934 MILLER 1300 x
Procedure, testing & result:
SQL> create or replace procedure p2 as
2 cursor c1 is select sal from test for update;
3 begin
4 for employee_rec in c1 loop
5 update test set
6 grade = case when employee_rec.sal > 3000 then 'A'
7 when employee_rec.sal > 2000 then 'B'
8 when employee_rec.sal > 1000 then 'C'
9 when employee_rec.sal <= 1000 then 'D'
10 end
11 where current of c1;
12 end loop;
13 end;
14 /
Procedure created.
SQL> exec p2;
PL/SQL procedure successfully completed.
SQL> select * From test order by sal desc;
EMPNO ENAME SAL G
---------- ---------- ---------- -
7839 KING 5000 A
7782 CLARK 2450 B
7934 MILLER 1300 C
SQL>