How to Refer Tablename.Column in IF

Question

Hi
I am new to PL/SQL programming
I have situation where I have to refer tablename.columnname
ex
psuedocode
if tablename .columnname exist Raise Exception F1
else if
process this block
end;
exception F1
Thanks,

Answer 1

there are some values in empno
My question is if the value in empno column already
matches with the user input
then raise exception
or else
process the block
if user inputs 4 it should raise exception
if user inputs 5 it should process else block
test@XE>
test@XE> @test
test@XE> --
test@XE> drop table emp;
Table dropped.
test@XE> create table emp (empno) as
  2  select rownum from all_objects
  3  where rownum <= 4;
Table created.
test@XE>
test@XE> --
test@XE> select * from emp;
     EMPNO
         1
         2
         3
         4
test@XE>
test@XE> --
test@XE> declare
  2    n_user_input      emp.empno%type;
  3    n_empno        emp.empno%type;
  4    e_value_exists exception;
  5  begin
  6    n_user_input := '&empno';
  7    select empno
  8    into n_empno
  9    from emp
10    where empno = n_user_input;
11    raise e_value_exists;
12  exception
13    when e_value_exists then
14      raise_application_error(-20001,'The input empno exists in emp table...');
15    when no_data_found then
16      -- go ahead and start processing
17      dbms_output.put_line('We shall start processing now...');
18  end;
19  /
Enter value for empno: 4
declare
ERROR at line 1:
ORA-20001: The input empno exists in emp table...
ORA-06512: at line 14
test@XE> /
Enter value for empno: 5
We shall start processing now...
PL/SQL procedure successfully completed.
test@XE>
test@XE> isotope