Oracle数据库之PL/SQL触发器

 1 plsql_trigger_source ::========
 2 
 3 [schema.] trigger_name
 4   { simple_dml_trigger
 5   | instead_of_dml_trigger
 6   | compound_dml_trigger
 7   | system_trigger
 8   }
 9 
10 simple_dml_trigger ::========
11 
12 { BEFORE | AFTER } dml_event_clause [ referencing_clause ] [ FOR EACH ROW ]
13   [ trigger_edition_clause ] [ trigger_ordering_clause ]
14     [ ENABLE | DISABLE ] [ WHEN ( condition ) ] trigger_body
15 
16 instead_of_dml_trigger ::=
17 
18 INSTEAD OF { DELETE | INSERT | UPDATE } [ OR { DELETE | INSERT | UPDATE } ]...
19 ON [ NESTED TABLE nested_table_column OF ] [ schema. ] noneditioning_view
20 [ referencing_clause ] [ FOR EACH ROW ]
21 [ trigger_edition_clause ] [ trigger_ordering_clause ]
22 [ ENABLE | DISABLE ] trigger_body
23 
24 system_trigger ::=======
25 
26 { BEFORE | AFTER | INSTEAD OF }
27 { ddl_event [OR ddl_event]...
28 | database_event [OR database_event]...
29 }
30 ON { [schema.] SCHEMA
31    | DATABASE
32    }
33 [ trigger_ordering clause ]
34 
35 dml_event_clause ::============
36 
37 { DELETE | INSERT | UPDATE [ OF column [, column ]... ] }
38 [ OR { DELETE | INSERT | UPDATE [ OF column [, column]... ] }...
39 ON [ schema.] { table | view }
40 
41 referencing_clause ::==========
42 
43 REFERENCING
44  { OLD [ AS ] old
45  | NEW [ AS ] new
46  | PARENT [ AS ] parent
47  }...
48 
49 trigger_body ::=======
50 
51 { plsql_block | CALL routine_clause }

1 CREATE OR REPLACE TRIGGER EMP_INSERT_ID
2 BEFORE INSERT ON employee FOR EACH ROW
3 BEGIN
4    SELECT SEQ_ID.NEXTVAL INTO :NEW.ID FROM DUAL;
5 END;

 1 示例2，在多表联接的视图中插入数据：
 2 
 3 -- 创建视图
 4 CREATE OR REPLACE VIEW vw_emp AS
 5 SELECT e.name ename, e.address, d.name dname
 6 FROM employee e, dept d
 7 WHERE e.did = d.id;
 8 
 9 -- 创建触发器
10 CREATE TRIGGER emp_insert_trigger
11    INSTEAD OF INSERT ON vw_emp
12 DECLARE
13    v_did dept.id%TYPE;
14 BEGIN
15    SELECT id INTO v_did FROM dept WHERE name = :NEW.dname;
16    INSERT INTO emp (name, address, did) VALUES (:NEW.ename, :NEW.address, v_did);
17 END emp_insert_trigger;

 1 示例3，创建实例启动触发器：
 2 
 3 -- 创建记录操作事件的表
 4 CREATE TABLE event_table(
 5    event VARCHAR2(50),
 6    time DATE
 7 );
 8 
 9 -- 创建触发器
10 CREATE OR REPLACE TRIGGER tr_startup
11    AFTER STARTUP
12    ON DATABASE
13 BEGIN
14    INSERT INTO event_table(event, time)
15     VALUES(ora_sysevent, SYSDATE);
16 END;

 1 CREATE OR REPLACE TRIGGER emp_sal_trigger
 2    BEFORE UPDATE OF salary OR DELETE
 3    ON employee FOR EACH ROW
 4    WHEN (old.did = 1)
 5 BEGIN
 6   CASE
 7      WHEN UPDATING (‘salary‘) THEN
 8         IF :NEW.salary < :old.salary THEN
 9            RAISE_APPLICATION_ERROR(-20001, ‘部门1的员工工资不能降‘);
10         END IF;
11      WHEN DELETING THEN
12           RAISE_APPLICATION_ERROR(-20002, ‘不能删除部门1的员工记录‘);
13   END CASE;
14 END emp_sal_trigger;

1 CREATE OR REPLACE TRIGGER emp_delete_trigger
2    INSTEAD OF DELETE ON vw_emp FOR EACH ROW
3 DECLARE
4    v_did dept.id%TYPE;
5 BEGIN
6    SELEC id INTO v_did FROM dept WHERE name=:OLD.dname;
7    DELETE FROM employee WHERE did= v_did;
8 END emp_delete_trigger;

 1 -- 创建记录用户登录注销日志的表
 2 CREATE TABLE log_on_off_log
 3 (user_name VARCHAR2(20),
 4  logon_date timestamp,
 5  logoff_date timestamp);
 6 
 7 -- 创建登录触发器
 8 CREATE OR REPLACE TRIGGER logon_trigger
 9    AFTER LOGON ON DATABASE
10 BEGIN
11    INSERT INTO log_on_off_log (user_name, logon_date) VALUES (ora_login_user, systimestamp);
12 END logon_trigger;
13 
14 -- 创建退出触发器
15 CREATE OR REPLACE TRIGGER logoff_trigger
16    BEFORE LOGOFF ON DATABASE
17 BEGIN
18    INSERT INTO log_on_off_log (user_name, logoff_date) VALUES (ora_login_user, systimestamp);
19 END logoff_trigger;