Tom, I am puzzled by Oracle behavior of triggers. I have created two same triggers on DEPT table and surprisingly they got compiled without errors. okay fine. then when I ran the update statement, it ran trigger 2 first and then trigger 1. 
So, how come it allows two same triggers? what is the use of that?
I also noticed that Oracle executing triggers in random order and not the order of creation [not that it is that important]

I was guessing Oracle will fail on second trigger while compiling but it did not.


SQL> desc dept;

 Name                Null?    Type
 ------              ------    ------
 DEPTNO             NOT NULL NUMBER(38)
 DNAME                       VARCHAR2(40)
 LOC                         VARCHAR2(40)


SQL> select trigger_name from user_triggers where table_name='DEPT';

no rows selected
                                                                                                                                                                                                                                                                                                                                                                                
SQL> select * from dept;

    DEPTNO DNAME                                    LOC                                                                 ---------- ---------------------------------------- ----------------------------------------                                    10 DepartmentName10                         Frankfort10                                                                 20 DepartmentName20                         Frankfort20                                                                 30 DepartmentName30                         Frankfort30                                                                 40 DepartmentName40                         Frankfort40                                                                 90 Finance                                  Lex                                                                        100 Finance                                  Lex                                                                        101 Finance                                  Lex                                                                                                                                                 

7 rows selected.


SQL>  create or replace trigger tr_bu_test1
  2  before update on dept for each row
  3  begin :new.dname:='from trigger2'; dbms_output.put_line('trigger 2'); end;
  4  /

Trigger created.

SQL> create or replace trigger tr_bu_test
  2  before update on dept for each row
  3   begin :new.dname:='from trigger1'; dbms_output.put_line('trigger 1'); end;
  4  /

Trigger created.

SQL> 
SQL> 
SQL> set serveroutput on;
SQL> update dept set dname='my name' where deptno=100;
trigger 2                                                                                                               trigger 1                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
1 row updated.

SQL> commit;

Commit complete.

SQL> select * from dept;

    DEPTNO DNAME                                    LOC                                                                 ---------- ---------------------------------------- ----------------------------------------                                    10 DepartmentName10                         Frankfort10                                                                 20 DepartmentName20                         Frankfort20                                                                 30 DepartmentName30                         Frankfort30                                                                 40 DepartmentName40                         Frankfort40                                                                 90 Finance                                  Lex                                                                        100 from trigger1                            Lex                                                                        101 Finance                                  Lex                                                                 
7 rows selected.