How use SYS_REFCURSUR in select for update in pl/sql - sql

Question

I want to select multiple rows and also update all selected rows. so this goal i wrote this query. but when execute it throw exception.
I wrote this query in a producer like bellow.
PROCEDURE get_rows(
a_cursor OUT SYS_REFCURSOR,
a_id IN VARCHAR,
a_count IN NUMBER);
exception detail:
java.sql.SQLException: ORA-01002: fetch out of sequence
a_cursor is SYS_REFCURSOR
OPEN a_cursor FOR
SELECT mytable.VID
FROM mytable
WHERE ROWNUM <= COUNT FOR UPDATE;
loop
FETCH a_cursor INTO a_id;
if a_cursor %notfound then
cnumber := 9999;
else
UPDATE mytable SET
...
WHERE VID = a_vid;
COMMIT;
end if;
end loop;

Answer 1

A sys_refcursor cannot be used in update statement. You can use an explicit cursor as shown below. Use this way:
DECLARE
cursor a_cursor is
SELECT mytable.VID
FROM mytable
WHERE ROWNUM <= COUNT FOR UPDATE;
a_id number;
begin
OPEN a_cursor;
loop
FETCH a_cursor INTO a_id;
exit when a_cursor%notfound;
UPDATE mytable SET
...
WHERE VID = a_vid;
end loop;
COMMIT;
close a_cursor;
end;
Edit:
create or replace PROCEDURE get_rows(
a_cursor OUT SYS_REFCURSOR,
a_id IN VARCHAR,
a_count IN NUMBER)
IS
cursor a_cur is
SELECT mytable.VID
FROM mytable
WHERE ROWNUM <= a_COUNT ;
a_id NUMBER;
cnumber number;
BEGIN
OPEN a_cur;
LOOP
FETCH a_cur INTO a_id;
IF a_cur%notfound THEN
cnumber := 9999;
End if;
exit when a_cursor%notfound;
UPDATE mytable SET
...
WHERE VID = a_vid;
END loop;
COMMIT;
CLOSE a_cur;
Open a_cursor for select * from mytable;
end ;

Answer 2

If you are not doing any other processing in the loop, you can use a MERGE statement instead of a cursor:
SQL Fiddle
Oracle 11g R2 Schema Setup:
CREATE TABLE mytable ( vid, columna ) AS
SELECT 1, 'a' FROM DUAL UNION ALL
SELECT 2, 'a' FROM DUAL UNION ALL
SELECT 3, 'a' FROM DUAL UNION ALL
SELECT 4, 'a' FROM DUAL UNION ALL
SELECT 5, 'a' FROM DUAL UNION ALL
SELECT 6, 'a' FROM DUAL;
Query 1:
MERGE INTO mytable dst
USING (
SELECT VID /* or ROWID AS rid */
FROM mytable
WHERE ROWNUM <= 3
) src
ON ( src.VID = dst.VID /* or src.RID = dst.ROWID */ )
WHEN MATCHED THEN
UPDATE SET
columna = 'b'
Query 2:
SELECT * FROM mytable
Results:
| VID | COLUMNA |
|-----|---------|
| 1 | b |
| 2 | b |
| 3 | b |
| 4 | a |
| 5 | a |
| 6 | a |