替代触发器的使用

当需要针对视图创建触发器来处理业务逻辑,或数据流程时, 可以用替代触发器来实现对视图相关表的操作.

SQL> create table user_info ( id number,name varchar2(200));

Table created.

SQL> insert into user_info values(1,'DINYA');

1 row created.

SQL> commit;

Commit complete.

SQL> create table skill( id number,skill varchar2(300),user_id number);

Table created.

SQL> insert into skill values(1,'打字',1);

1 row created.

SQL> commit;

Commit complete.

SQL> create or replace view user_skills as select a.id ,a.name,b.skill from user_info a,skill b wher
e a.id=b.user_id;

View created.

SQL> select * from user_skills;

ID NAME SKILL
--------------- -------------------------------- -----------------------------------------------
1 DINYA 打字

SQL> update user_skills t set t.skill='上网' ;
update user_skills t set t.skill='上网'
*
ERROR at line 1:
ORA-01779: cannot modify a column which maps to a non key-preserved table

SQL> create or replace trigger user_skills_update
2 instead of update on user_skills
3 for each row
4 begin
5 update skill set skill=:new.skill where user_id=:old.id;
6 end ;
7 /

Trigger created.

SQL> update user_skills t set t.skill='上网' where t.id=1;

1 row updated.

SQL> commit;

Commit complete.

SQL> select * from skill;

ID SKILL USER_ID
----------------- --------------------- ---------------------------------------------------------
1 上网 1

SQL>

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Dinya