/*===
    PROOF of CONCEPT: our first trigger!

    trigger: empl_trig: before update on empl

    purpose: if serveroutput is set to on,
        before each update ***of a row*** in empl,
        prints a message to the screen
===*/

create or replace trigger empl_trig
    before update
    on empl
    for each row
begin
    dbms_output.put_line('=======================');
    dbms_output.put_line('ABOUT to update an empl row!');
end;
/
show errors

set serveroutput on

prompt
prompt ========
prompt exercising trigger1.sql's FIRST version of trigger empl_trig

commit;

prompt ========
prompt SHOULD see messages about updating empl rows,
prompt one message per row updated:
prompt

update empl
set hiredate = sysdate;

prompt contents of empl after updates (and before rollback!):
prompt ========

select *
from   empl;

rollback;