INPUT
declare
          no number(5);
          bal number(6);
          deb_bal number(6);
          min_bal constant number(5):=500;

begin
          no:=&no;
          deb_bal:=&deb_bal;
          select balance into bal from acc where acc_no=no;
          if bal>min_bal then
                   update acc set balance=balance-deb_bal where acc_no=no;
                   dbms_output.put_line('debit sucessfully');
          else
                   dbms_output.put_line('you have not minimum balance');
          end if;

end;

OUTPUT
1)
Enter value for no: 1201
old   8:  no:=&no;
new   8:  no:=1201;
Enter value for deb_bal: 1000
old   9:  deb_bal:=&deb_bal;
new   9:  deb_bal:=1000;
debit sucessfully
PL/SQL procedure successfully completed.


2)
Enter value for no: 1202
old   8:  no:=&no;
new   8:  no:=1202;
Enter value for deb_bal: 100
old   9:  deb_bal:=&deb_bal;
new   9:  deb_bal:=100;
you have not minimum balance
PL/SQL procedure successfully completed.