A numeric variable with no specified size, no initial value
SQL>
SQL> -- A numeric variable with no specified size.
SQL> -- No initial value.
SQL> -- x has the value NULL.
SQL>
SQL> set serverout on;
SQL>
SQL> DECLARE
2 X NUMBER;
3 BEGIN
4
5 DBMS_OUTPUT.PUT_LINE(x);
6 END;
7 /