Performance: Cursor declaration versus explicit query in BEGIN/END block

Question

Hi guys!
Anyone knows if declare an explicit cursor inside a pl/sql block is faster than using a cursor declaration, and how fast it its?
Which block runs faster? And how fast? ( once, twice, once and a half ? )
Block1:
DECLARE
CURSOR cur_test (p1 NUMBER) IS
SELECT field1, field2 FROM table WHERE field0 = p1;
vf1 VARCHAR2(1)
vf2 NUMBER;
n NUMBER := 0;
BEGIN
OPEN cur_test ( n );
FETCH cur_test INTO vf1, vf2;
CLOSE cur_test;
END;
Block2:
DECLARE
vf1 VARCHAR2(1)
vf2 NUMBER;
n NUMBER := 0;
BEGIN
BEGIN
SELECT field1, field2
INTO vf1, vf2
FROM table WHERE field0 = n;
EXCEPTION
WHEN others THEN
null;
END;
END;
I have LOOP in a cursor and may open/fetch/closes in this loop. I´m wondering how fast would it be if I change the open/fetch/closes to explicit query blocks...
Thanks!
Murilo

Answer 1

If you expect your qurey to return a single row, you would generally want to use a SELECT ... INTO. You'd only want to use a cursor if you expect to return multiple rows of data.
If you are doing this in a loop, I would strongly suspect that you should be letting Oracle join the tables in SQL rather than doing your own pseudo-join logic in PL/SQL. Letting SQL do the work of joining tables is going to generally be a sustantial performance difference. The difference between the two blocks you posted will be marginal at best.
Justin
Distributed Database Consulting, Inc.
http://www.ddbcinc.com/askDDBC