Error: cursor already open in nested for loops - for-loop

Question

create or replace PROCEDURE template2(
template_id_in IN RTEMPLATE_CONFIGURE.TEMPLATE_ID%TYPE)
AS
source_table rtemplate_configure.sobject_name%type;
source_column rtemplate_configure.scolumn_name%type;
target_table rtemplate_configure.tobject_name%type;
target_column rtemplate_configure.tcolumn_name%type;
tmp VARCHAR2(2000);
tmp2 VARCHAR2(2000);
CURSOR c_template_configure is
SELECT * FROM rtemplate_configure WHERE template_id = template_id_in order by source_table, target_table;
BEGIN
FOR record_line in c_template_configure LOOP
FOR record_line2 in c_template_configure LOOP
IF record_line.sobject_name = record_line2.sobject_name
and record_line.tobject_name = record_line2.tobject_name
and record_line.tcolumn_name <> record_line2.tcolumn_name
and record_line.scolumn_name <> record_line2.scolumn_name
THEN
tmp2 := 'INSERT INTO '||record_line.tobject_name||'('||record_line.tcolumn_name||','||record_line2.tcolumn_name||')'||'
SELECT '||record_line.scolumn_name||','||record_line.scolumn_name||'
FROM '||record_line.sobject_name||'';
DBMS_OUTPUT.put_line
(tmp2);
END IF;
END LOOP;
END LOOP;
--COMMIT;
END template2;
I am getting error: PL/SQL: cursor already open, and I closed it properly, I guess? I am not sure if I used for loops properly as well, I just need that one cursor to go through the nested loops to check the data as seen in if statement.

Answer 1

You have opened cursor c_template_configure twice. You can't do that, you'll need to create a copy e.g. c_template_configure2.
Here is a very simple example of what you have done:
SQL> declare
2 cursor c is select * from emp;
3 begin
4 for r1 in c loop -- Open cursor c once
5 for r2 in c loop -- Open cursor c again, already open
6 null;
7 end loop;
8 end loop;
9 end;
10 /
declare
*
ERROR at line 1:
ORA-06511: PL/SQL: cursor already open
ORA-06512: at line 2
ORA-06512: at line 5
Now here is the corrected code:
1 declare
2 cursor c1 is select * from emp;
3 cursor c2 is select * from emp;
4 begin
5 for r1 in c1 loop
6 for r2 in c2 loop
7 null;
8 end loop;
9 end loop;
10* end;
SQL> /
Aside: If processing a lot of data, this is a very inefficient approach. Consider joining the data in the query for example:
select e1.empno as empno1, e2.empno as empno2
from emp e1
cross join emp e2
where e1.empno != e2.empno;
Now you only have 1 cursor to open and it returns all the pairs of employees.

Answer 2

declare
cursor c1 is
select *from emp;
r1 c1%rowtype;
begin
open c1;
fetch c1 into r1;
close c1;
null;
commit;
end;