sql plus warning in procedure. procedure created with compilation error. (procedure with parameter) - oracle

Question

hey i am trying to do a pl sql program with the help of procedure. i want to check if number given by user is even or odd using procedure but i am getting an warning : procedure created with compilation error .
create or replace procedure even( a in out number)
as n number :=&n;
begin
if(n,2)=0 then
dbms_output.put_line('even');
else
dbms_output.put_line('odd');
end if;
end;
/

Answer 1

It is meaningless to compile the procedure each time you get user input.You should rather be doing the following.
Compile the procedure without any substitution variables. The parameter should be just IN and not IN OUT unless you want to modify its value inside the procedure.
CREATE OR replace PROCEDURE Even(n IN NUMBER)
AS
BEGIN
IF MOD(n, 2) = 0 THEN
dbms_output.put_line('even');
ELSE
dbms_output.put_line('odd');
END IF;
END;
/
Then execute this compiled procedure as many times as you like by passing user input.
SQL> SET SERVEROUTPUT ON;
SQL> EXEC even ( &n );
Enter value for n: 5
odd
PL/SQL procedure successfully completed.
SQL> EXEC even ( &n );
Enter value for n: 4
even
PL/SQL procedure successfully completed.

Answer 2

Why don't you use you mod function:
if mod(a,2)=0 then
dbms_output.put_line('even');
else
dbms_output.put_line('odd');
end if;
I think you put "n" instead of "a"

Answer 3

Consider using a function instead; in my opinion, it is a better option for such a task than a procedure.
A natural choice would be a function that returns Boolean:
SQL> create or replace function f_is_even (par_n in number)
2 return boolean
3 is
4 begin
5 return mod(par_n, 2) = 0;
6 end;
7 /
Function created.
You'd then use it in some PL/SQL code as the following example (yes, it looks stupid because it appears that it does exactly what your procedure does, but note - this is just an example; in real life, you'd use it in smarter way):
SQL> begin
2 if f_is_even(6) then
3 dbms_output.put_Line('even');
4 else
5 dbms_output.put_Line('odd');
6 end if;
7 end;
8 /
even
PL/SQL procedure successfully completed.
Drawback of such a function is that you can't use it in SQL (but, as I said, PL/SQL):
SQL> select f_is_even(5) from dual;
select f_is_even(5) from dual
*
ERROR at line 1:
ORA-06552: PL/SQL: Statement ignored
ORA-06553: PLS-382: expression is of wrong type
A possible "workaround" is to create a procedure that doesn't return Boolean but, for example, number (0 for "false" and 1 for "true") or string (N for "false, no" and Y for "true, yes"). For example:
SQL> create or replace function f_is_even_01 (par_n in number)
2 -- returns 1 if number is even; returns 0 if number is odd
3 return number
4 is
5 begin
6 return case when mod(par_n, 2) = 0 then 1
7 else 0
8 end;
9 end;
10 /
Function created.
SQL> select f_is_even_01(5) r1,
2 f_is_even_01(6) r2
3 from dual;
R1 R2
---------- ----------
0 1
There's nothing wrong in using a procedure; I just thought that you might want to hear another opinion.