Cursor Parameter List

Question

Hi,
recently I found out that a cursor must not have explicit a defined parameter list:
1. Option
cursor cur_example
is
select name
from table1
where name = p_name
=> instead of
2. Option
cursor cur_example (p_name IN VARCHAR2)
is
select name
from table1
where name = p_name
why is then sometimes a parameterlist definition necessary?
cheers,
Bernhard

Answer 1

> my problem is to understand if a parameter list must not necessarily be defined? But if it is defined it seems that it is only for readability reasons!!!!!????
True. In programming generally we often have the choice of whether to pass a parameter or have the code refer to a global variable, and passing the parameter is nearly always better practice because it makes the dependency explicit and therefore easier to understand. For example, this sort of scenario is ambiguous without cursor parameters:
DECLARE
    v_somevar VARCHAR2(1) := 'X';
    v_count INTEGER;
    CURSOR c IS
        SELECT COUNT(*) FROM dual WHERE dummy = v_somevar;
BEGIN
    v_somevar := 'Y';
    OPEN c;
    FETCH c INTO v_count;
    CLOSE c;
    DBMS_OUTPUT.PUT_LINE('Count = ' || v_count);
END;I would always prefer the equivalent,
DECLARE
    v_somevar VARCHAR2(1) := 'X';
    v_count INTEGER;
    CURSOR c ( cp_someval dual.dummy%TYPE ) IS
        SELECT COUNT(*) FROM dual WHERE dummy = cp_someval;
BEGIN
    v_somevar := 'Y';
    OPEN c (v_somevar);
    FETCH c INTO v_count;
    CLOSE c;
    DBMS_OUTPUT.PUT_LINE('Count = ' || v_count);
END;