pl/sql trigger

  1 SQL> create or replace trigger my_trigger after update on scott.a for each row
  2   2  begin
  3   3      update scott.c set dep=:new.departno
  4   4      where dep=:old.departno;
  5   5  end;
  6   6  /
  7 
  8 --the occasion before running the trigger
  9 SQL> select * from a
 10   2  /
 11  
 12   DEPARTNO DEPARTNAME NUM(PK)
 13 ---------- --------------------
 14        100 部门一  1
 15        200 部门二  2
 16        300 部门三  3
 17  
 18 SQL> select * from c
 19   2  /
 20  
 21       C_NO C_NAME                      DEP
 22 ---------- -------------------- ----------
 23          1 1                           100
 24          2 2                           200
 25 
 26 --run the create trigger sentence
 27 create or replace trigger my_trigger after update on scott.a for each row
 28 begin
 29     update scott.c set dep=:new.departno
 30     where dep=:old.departno;
 31 end;
 32 
 33 Trigger created
 34 
 35 --trigger the constrain and the event will be executed.
 36 SQL> update a set departno=500 where departno=100;
 37 
 38 --you can refer to the following result:
 39 SQL> select * from a
 40   2  /
 41  
 42   DEPARTNO DEPARTNAME                  NUM
 43 ---------- -------------------- ----------
 44        500 部门一                        1
 45        200 部门二                        2
 46        300 部门三                        3
 47  
 48 SQL> select * from c
 49   2  /
 50  
 51       C_NO C_NAME                      DEP
 52 ---------- -------------------- ----------
 53          1 1                           500
 54          2 2                           200
 55 
 56 ---after insert，then we only read :new 
 57 create or replace trigger my_trigger after insert on a for each row
 58 begin
 59 dbms_output.put_line(:new.departno);
 60 end;
 61 
 62 ---after update，then we read both :old and :new 
 63 create or replace trigger my_trigger after update on a for each row
 64 begin
 65 dbms_output.put_line(:old.departno);
 66 dbms_output.put_line(:new.departno);
 67 end;
 68 
 69 ---after delete，then we only read :old 
 70 create or replace trigger my_trigger after delete on a for each row
 71 begin
 72 dbms_output.put_line(:old.departno);
 73 end;
 74 
 75 
 76 --create a trigger and to log the date
 77 --There are two tables: t_trigger_test01,t_trigger_log
 78 drop table t_trigger_test01;
 79 create table t_trigger_test01(
 80 id integer primary key,
 81 name varchar2(20)
 82 );
 83 drop table t_trigger_log;
 84 create table t_trigger_log(
 85 action_date date,
 86 action varchar2(20)
 87 );
 88 create or replace trigger log_trigger
 89 after insert or update or delete on t_trigger_test01
 90 declare
 91   v_action varchar2(20);
 92 begin
 93   if inserting then v_action:='insert';
 94   elsif updating then v_action:='update';
 95   elsif deleting then v_action:='delete';
 96   else dbms_output.put_line('..');
 97   end if;
 98   insert into t_trigger_log values(sysdate, v_action);
 99 end;
100 
101 --create a rwo trigger to update a corresponding table when the colume value is changed
102 --two tables: t_class,t_student
103 drop table t_trigger_class;
104 create table t_trigger_class(
105 id number(10,0) primary key,
106 name varchar2(20)
107 );
108 drop table t_trigger_student;
109 create table t_trigger_student(
110 sno integer primary key,
111 name varchar2(20),
112 cno number(10,0)
113 );
114 
115 create or replace trigger row_trigger after update on t_trigger_class for each row
116 begin
117     update t_trigger_student set cno=:new.id
118     where cno=:old.id;
119 end;
120 /
121 
122 --create instead of tirgger
123 drop view v_trigger_stu_class;
124 create view v_trigger_stu_class
125 as
126 select c.id,c.name as cname,s.sno,s.name as sname,s.cno from scott.t_trigger_class c, scott.t_trigger_student s
127 where s.cno=c.id;
128 
129 
130 create or replace trigger instead_of_trigger
131 instead of update on v_trigger_stu_class
132 begin
133       update scott.t_trigger_class c set c.id=:new.id,c.name=:new.cname
134       where c.id=:old.id;
135       update scott.t_trigger_student s set s.sno=:new.sno,s.name=:new.sname,s.cno=:new.cno
136       where s.sno=:old.sno;
137 end;
138