Using select * in pl/sql

Question

Hi,
Yesterday Karthick mentioned that using SELECT * in PL/SQL is not a good idea. But I tried by creating a table and different procedures with selecting all columns using * and specifying the columns individually. Later I altered the table and both procedures became invalid. Can some one give a simple example to demonstrate the behaviour.
At present I dont have Oracle in my PC to post what I have tried yesterday.
Cheers,
Suri

Answer 1

When I run the following script, the 2nd time the test1 procedure runs, it fails with "PLS-00905: object TEST1 is invalid", whereas test2 runs fine both times.
Feel free to try it yourself!
create table boneist_test (col1 number, col2 varchar2(10));
insert into boneist_test values (1, 'a');
commit;
create procedure test1
is
  v_num number;
  v_var varchar2(10);
begin
  select *
  into v_num, v_var
  from boneist_test
  where rownum = 1;
end test1;
create procedure test2
is
  v_num number;
  v_var varchar2(10);
begin
  select col1, col2
  into v_num, v_var
  from boneist_test
  where rownum = 1;
end test2;
begin
  test1;
end;
begin
  test2;
end;
alter table boneist_test add (col3 number);
begin
  test1;
end;
begin
  test2;
end;
drop table boneist_test;
drop procedure test1;
drop procedure test2;