上一篇对触发器的一些基本知识有了了解，在这一篇操作进行验证
before触发器
[oracle@test ~]$ sqlplus / as sysdba
SQL> create user trigger_test identified by 123456 ;
SQL> grant create session to trigger_test ;
SQL> grant create table to trigger_test ;
SQL> grant dba to trigger_test ;
SQL> grant resource to trigger_test ；
SQL> grant create sequence to trigger_test ;[oracle@test ~]$ sqlplus trigger_test/123456
创建测试表student
SQL> create table student(STUDENT_ID NUMBER(8),name varchar2(15),CREATED_BY VARCHAR2(30) not null,CREATED_DATE DATE not null,MODIFIED_BY VARCHAR2(30) not null,MODIFIED_DATE DATE not null)创建序列student_id_seq
create sequence student_id_seq
minvalue 1
maxvalue 9999999999999999999999999999
start with 100
increment by 1;SQL> select * from student ;
no rows selected
SQL> select * from cat ;
TABLE_NAME TABLE_TYPE
------------------------------ -----------
STUDENT TABLE
STUDENT_ID_SEQ SEQUENCEcreate or replace trigger student_before_insert
before insert on student
for each row
declare
v_student_id student.student_id%type ;
begin
select student_id_seq.nextval
into v_student_id
from dual ;
:new.student_id := v_student_id ;
:new.created_by := user ;
:new.created_date := sysdate ;
:new.modified_by := user ;
:new.modified_date := sysdate ;
end;SQL> insert into student (name) values ('mjt');
SQL> commit ;
SQL> select * from student ;
STUDENT_ID NAME CREATED_BY CREATED_DATE
---------- --------------- ------------------------------ -------------------
MODIFIED_BY MODIFIED_DATE
------------------------------ -------------------
100 mjt TRIGGER_TEST 2015-07-29 20:51:19
TRIGGER_TEST 2015-07-29 20:51:19
SQL> insert into student (name) values ('cxq') ;
1 row created.
SQL> select * from student ;
STUDENT_ID NAME CREATED_BY CREATED_DATE
---------- --------------- ------------------------------ -------------------
MODIFIED_BY MODIFIED_DATE
------------------------------ -------------------
100 mjt TRIGGER_TEST 2015-07-29 20:51:19
TRIGGER_TEST 2015-07-29 20:51:19
101 cxq TRIGGER_TEST 2015-07-29 21:00:54
TRIGGER_TEST 2015-07-29 21:00:54after触发器
SQL> create table record(table_name varchar2(30),transaction_name varchar2(10),transaction_user varchar2(30),transaction_date date);这个表被用来记录数据库中不同表的信息，如，可以记录谁从student表中删除或者更新数据，以及记录时间。
下面的触发器针对对student表的更新或者删除操作，在此之后进行触发
create or replace trigger student_aud
after update or delete on student
declare
v_type varchar2(10);
begin
if updating then
v_type := 'UPDATE';
elsif deleting then
v_type := 'DELETE';
end if;
update trigger_test.record
set transaction_user = user,
transaction_date = sysdate
where table_name = 'student'
and transaction_name = v_type;
if sql%notfound then
insert into trigger_test.record values ('student', v_type, user, sysdate);
end if;
end;SQL> select * from record ;
no rows selected
SQL> select * from student ;
STUDENT_ID NAME CREATED_BY CREATED_DATE
---------- --------------- ------------------------------ -------------------
MODIFIED_BY MODIFIED_DATE
------------------------------ -------------------
100 mjt TRIGGER_TEST 2015-07-29 20:51:19
TRIGGER_TEST 2015-07-29 20:51:19
101 cxq TRIGGER_TEST 2015-07-29 21:00:54
TRIGGER_TEST 2015-07-29 21:00:54
SQL> update student set name = 'somebody' where name = 'mjt' ;
1 row updated.
SQL> commit ;
Commit complete.
SQL> select * from student ;
STUDENT_ID NAME CREATED_BY CREATED_DATE
---------- --------------- ------------------------------ -------------------
MODIFIED_BY MODIFIED_DATE
------------------------------ -------------------
100 somebody TRIGGER_TEST 2015-07-29 20:51:19
TRIGGER_TEST 2015-07-29 20:51:19
101 cxq TRIGGER_TEST 2015-07-29 21:00:54
TRIGGER_TEST 2015-07-29 21:00:54
SQL> select * from record ;
TABLE_NAME TRANSACTIO TRANSACTION_USER
------------------------------ ---------- ------------------------------
TRANSACTION_DATE
-------------------
student UPDATE TRIGGER_TEST
2015-07-29 21:50:46
SQL> delete student where name = 'somebody' ;
1 row deleted.
SQL> commit ;
Commit complete.
SQL> select * from student ;
STUDENT_ID NAME CREATED_BY CREATED_DATE
---------- --------------- ------------------------------ -------------------
MODIFIED_BY MODIFIED_DATE
------------------------------ -------------------
101 cxq TRIGGER_TEST 2015-07-29 21:00:54
TRIGGER_TEST 2015-07-29 21:00:54
SQL> select * from record ;
TABLE_NAME TRANSACTIO TRANSACTION_USER
------------------------------ ---------- ------------------------------
TRANSACTION_DATE
-------------------
student UPDATE TRIGGER_TEST
2015-07-29 21:50:46
student DELETE TRIGGER_TEST
2015-07-29 21:56:08
SQL> alter trigger student_aud disable ;
Trigger altered.
SQL> update student set name = 'mjt' where name = 'cxq';
1 row updated.
SQL> commit ;
Commit complete.
SQL> select * from student ;
STUDENT_ID NAME CREATED_BY CREATED_DATE
---------- --------------- ------------------------------ -------------------
MODIFIED_BY MODIFIED_DATE
------------------------------ -------------------
101 mjt TRIGGER_TEST 2015-07-29 21:00:54
TRIGGER_TEST 2015-07-29 21:00:54
SQL> select * from record ;
TABLE_NAME TRANSACTIO TRANSACTION_USER
------------------------------ ---------- ------------------------------
TRANSACTION_DATE
-------------------
student UPDATE TRIGGER_TEST
2015-07-29 21:50:46
student DELETE TRIGGER_TEST
2015-07-29 21:56:08禁用触发器之后，在student表上的update操作不再触发产生记录到record表
对应启用
SQL> alter trigger student_aud enable ;
Trigger altered.3.自治事务
自治事务是由其他事务(通常被称为主事务)发起的独立事务，自治事务也许会执行多个dml语句，并且提交或者回滚，而不会提交或者回滚主事务执行的dml语句。
假如希望即使主事务失败，仍旧能够记录审计数据，这种情况下，主事务是面向
表的update或者delete，需要定义可以独立于主事务进行提交的自治事务。
定义主事务，需要使用autonomous_transaction编译指令在语句块的声明部分
declare
pragma autonomous_transaction
commit ;
create or replace trigger student_aud
after update or delete on student
declare
v_type varchar2(10);
pragma autonomous_transaction ;
begin
if updating then
v_type := 'UPDATE';
elsif deleting then
v_type := 'DELETE';
end if;
update trigger_test.record
set transaction_user = user,
transaction_date = sysdate
where table_name = 'student'
and transaction_name = v_type;
if sql%notfound then
insert into trigger_test.record values ('student', v_type, user, sysdate);
end if;
commit ;
end;如果当前更新或者删除表student中的内容，无论成功或者失败，都会在record表中记录当前的操作。不足的是，record表中最多只能记录两条数据，只是当前最新操作的时间以及操作者。
