Cursor not found - postgresql

Question

i have created procedure, inside used cursor to update the some data, while calling the procedure it's getting the error.
create or REPLACE PROCEDURE bal_upd(p_id int) as
$$
DECLARE rc record;
----- cursor
bal_upd1 CURSOR (p_id int)
for
select * from tbal where custid = p_id;
begin
open bal_upd1 (p_id);
loop
FETCH bal_upd1 into rc;
exit when not found;
update t_trans set balance = balance + rc.trans;
COMMIT;
end loop;
close bal_upd1;
end;
$$ LANGUAGE plpgsql;
call bal_upd(1)
ERROR: cursor "bal_upd1" does not exist
CONTEXT: PL/pgSQL function bal_upd(integer) line 12 at FETCH
SQL state: 34000
create or REPLACE PROCEDURE bal_upd(p_id int) as
$$
DECLARE rc record;
----- cursor
bal_upd1 CURSOR (p_id int)
for
select * from tbal where custid = p_id;
begin
open bal_upd1 (p_id);
loop
FETCH bal_upd1 into rc;
exit when not found;
update t_trans set balance = balance + rc.trans;
COMMIT;
end loop;
close bal_upd1;
end;
$$ LANGUAGE plpgsql;
call bal_upd(1)
ERROR: cursor "bal_upd1" does not exist
CONTEXT: PL/pgSQL function bal_upd(integer) line 12 at FETCH
SQL state: 34000

Answer 1

You don't need a function or a loop for that:
UPDATE t_trans
SET balance = t_trans.balance + t.trans
FROM (SELECT sum(trans) AS trans
FROM tbal
GROUP BY custid) AS t
WHERE t_trans.custid = t.custid;

Answer 2

I tried, failed. I just found just use for loop (implicit cursor) is far more simple.
BEGIN;
CREATE temp TABLE tbal (
custid bigint
, trans numeric
);
INSERT INTO tbal VALUES (1 , 1);
INSERT INTO tbal VALUES (1 , 2);
CREATE temp TABLE t_trans (
custid bigint
, balance numeric
);
INSERT INTO t_trans VALUES (1 , 10);
COMMIT;
CREATE OR REPLACE PROCEDURE bal_upd (bigint)
AS $func$
DECLARE
rc record;
BEGIN
FOR rc IN
SELECT
*
FROM
tbal
WHERE
custid = $1 LOOP
RAISE NOTICE 'custid: %, trans: % ' , rc.custid , rc.trans;
UPDATE
t_trans ta
SET
balance = balance + (rc.trans)
WHERE
ta.custid = (rc.custid);
END LOOP;
END;
$func$
LANGUAGE plpgsql;
Then call it. CALL bal_upd(1);