Basic cursor question

Question

When does the select statement in a cursor get execute?
Is it when the program gets parsed during execution or when the cursor is opened.
Thanks
MD

Answer 1

FrancisC_1 wrote:
Would both queries for c1 and c2 be executed? Maybe it's more subtle than that and the queries might be parsed but no data actually fetched?
I don't know if it matters, but I'm on version 9i.
Any insight will be appreciated.In short. No.
The cursor definitions in the declaration section do not cause "execution" of the cursors. This only happens when, you open the cursor, which in your case is done when the relevant FOR loop is started.
Example:
SQL> ed
Wrote file afiedt.buf
  1  CREATE OR REPLACE PROCEDURE p1 (param1 IN VARCHAR2) IS
  2    CURSOR c1 IS
  3      SELECT empno
  4      FROM emp
  5      WHERE empno = to_number(param1);
  6  BEGIN
  7    DBMS_OUTPUT.PUT_LINE('Pre-Open');
  8    FOR r IN c1 LOOP
  9       DBMS_OUTPUT.PUT_LINE(r.empno);
10    END LOOP;
11    DBMS_OUTPUT.PUT_LINE('Post-Close');
12  EXCEPTION
13    WHEN OTHERS THEN
14      DBMS_OUTPUT.PUT_LINE('Exception');
15      RAISE;
16* END;
SQL> /
Procedure created.
SQL> set serverout on;
SQL> exec p1('7788');
Pre-Open
7788
Post-Close
PL/SQL procedure successfully completed.
SQL> exec p1('77xx');
Pre-Open
Exception
BEGIN p1('77xx'); END;
ERROR at line 1:
ORA-01722: invalid number
ORA-06512: at "SCOTT.P1", line 15
ORA-06512: at line 1
SQL>As you can see, when an invalid number was passed in, this didn't cause an exception to happen within the declaration section, but only when the FOR loop was started, so the actual execution of the query (that would try to convert the parameter to a number) only happened then, not during the declaration.
As your procedure is designed to run one FOR loop or the other depending on the parameter, only the one relevant query will be executed.