PL/SQL: I get expression 'I' cannot be used as an assignment target - plsql

Question

My code:
create table info(str varchar2(30));
declare
cursor c(job emp_ast.job_id%type, dep emp_ast.department_id%type) is select employee_id
from emp_ast
where job_id=job and department_id=dep;
type t_job is table of emp_ast.job_id%type;
t t_job:=t_job();
emp emp_ast.employee_id%type;
i number(3);
begin
select job_id
bulk collect into t
from emp_ast;
for i in 10..270 loop
for j in 1..t.count loop
open c(i, t(j));
loop
fetch c into emp;
insert into info
values (i||' '||t(j)||' '||emp);
exit when c%notfound;
end loop;
i:=i+10;
end loop;
end loop;
end;
/
I get "expression 'I' cannot be used as an assignment target", reffering to the line where I increment i by 10. I am trying to save the department_id, employee_id and job_id as a string in a table for each department and each job.

Answer 1

At the point where you get that message, i refers to the loop control variable i defined in the line for i in 10..270 loop, not the int(3) variable defined earlier. In PL/SQL a loop definition defines a variable which is only accessible inside the loop, and which you cannot alter. I suggest you change the name of one or the other to make them unique.
EDIT
PL/SQL doesn't provide a way to step by more than 1 in a computed FOR loop. Instead, you will need to compute the desired department number value within the loop:
DECLARE
CURSOR c(job EMP_AST.JOB_ID%TYPE,
dep EMP_AST.DEPARTMENT_ID%TYPE)
IS SELECT EMPLOYEE_ID
FROM EMP_AST
WHERE JOB_ID = job AND
DEPARTMENT_ID = dep;
TYPE t_job IS TABLE OF EMP_AST.JOB_ID%TYPE;
t t_job := t_job();
emp EMP_AST.EMPLOYEE_ID%TYPE;
nDepartment NUMBER;
BEGIN
SELECT job_id
BULK COLLECT INTO t
FROM EMP_AST;
FOR i IN 1..27 LOOP
nDepartment := i * 10;
FOR j IN 1..t.COUNT LOOP
OPEN c(t(j), nDepartment);
LOOP
FETCH c INTO emp;
INSERT INTO info
VALUES (nDepartment || ' ' || t(j) || ' ' || emp);
EXIT WHEN c%notfound;
END LOOP; -- cursor c
CLOSE c;
END LOOP; -- j
END LOOP; -- i
END;
/
Note that in the code above the nDepartment value is computed within the i loop, which now increments from 1 to 27 instead of going from 10 to 270.