openGauss每日一练第18天|触发器

学习目标

学习openGauss触发器

触发器是对应用动作的响应机制，当应用对一个对象发起DML操作时，就会产生一个触发事件（Event），如果该对象上拥有该事件对应的触发器，那么就会检查触发器的触发条件（Condition）是否满足，如果满足触发条件，那么就会执行触发动作（Action）

课程学习

连接数据库

#第一次进入等待15秒

#数据库启动中...

su - omm

gsql -r

1.创建源表及触发表

CREATE TABLE test_trigger_src_tbl(id1 INT, id2 INT, id3 INT) ;

CREATE TABLE test_trigger_des_tbl(id1 INT, id2 INT, id3 INT);

2.insert触发器

–创建触发器函数

CREATE OR REPLACE FUNCTION tri_insert_func() RETURNS TRIGGER AS

$$

DECLARE

BEGIN

INSERT INTO test_trigger_des_tbl VALUES(NEW.id1, NEW.id2, NEW.id3);

RETURN NEW;

END

$$ LANGUAGE PLPGSQL;

–创建INSERT触发器

CREATE TRIGGER insert_trigger

BEFORE INSERT ON test_trigger_src_tbl

FOR EACH ROW

EXECUTE PROCEDURE tri_insert_func();

–执行INSERT触发事件并检查触发结果

INSERT INTO test_trigger_src_tbl VALUES(100,200,300);

–查看触发操作生效

SELECT * FROM test_trigger_src_tbl;

SELECT * FROM test_trigger_des_tbl;

3.update触发器

–创建触发器函数

CREATE OR REPLACE FUNCTION tri_update_func() RETURNS TRIGGER AS

$$

DECLARE

BEGIN

UPDATE test_trigger_des_tbl SET id3 = NEW.id3 WHERE id1=OLD.id1;

RETURN OLD;

END

$$ LANGUAGE PLPGSQL;

–创建update触发器

CREATE TRIGGER update_trigger

AFTER UPDATE ON test_trigger_src_tbl

FOR EACH ROW

EXECUTE PROCEDURE tri_update_func();

–执行update触发事件并检查触发结果

UPDATE test_trigger_src_tbl SET id3=400 WHERE id1=100;

–查看触发操作生效

SELECT * FROM test_trigger_src_tbl;

SELECT * FROM test_trigger_des_tbl;

4.delete触发器

–创建触发器函数

CREATE OR REPLACE FUNCTION TRI_DELETE_FUNC() RETURNS TRIGGER AS

$$

DECLARE

BEGIN

DELETE FROM test_trigger_des_tbl WHERE id1=OLD.id1;

RETURN OLD;

END

$$ LANGUAGE PLPGSQL;

–创建delete触发器

CREATE TRIGGER delete_trigger

BEFORE DELETE ON test_trigger_src_tbl

FOR EACH ROW

EXECUTE PROCEDURE tri_delete_func();

–执行delete触发事件并检查触发结果

DELETE FROM test_trigger_src_tbl WHERE id1=100;

–查看触发操作生效

SELECT * FROM test_trigger_src_tbl;

SELECT * FROM test_trigger_des_tbl;  

5.修改触发器

–重命名

ALTER TRIGGER delete_trigger ON test_trigger_src_tbl RENAME TO delete_trigger_renamed;

–在系统表PG_TRIGGER中查看触发器

select * from PG_TRIGGER;

–查看表上的所有触发器

\dS+ test_trigger_src_tbl

6.禁用触发器

–禁用insert_trigger触发器

ALTER TABLE test_trigger_src_tbl DISABLE TRIGGER insert_trigger;

–执行INSERT

INSERT INTO test_trigger_src_tbl VALUES(100,200,300);

–查看触发操作没有生效

SELECT * FROM test_trigger_src_tbl;

SELECT * FROM test_trigger_des_tbl;

–禁用当前表上所有触发器

ALTER TABLE test_trigger_src_tbl DISABLE TRIGGER ALL;

7.删除触发器

DROP TRIGGER update_trigger ON test_trigger_src_tbl;

DROP TRIGGER delete_trigger_renamed ON test_trigger_src_tbl;     

课程作业

1.创建源表和触发表，在源表上创建insert触发器，创建操作触发表的触发器函数

omm=# create table source_table (id int);

CREATE TABLE

omm=# create table target_table (id int);

CREATE TABLE

omm=# 



omm=# create or replace function tri_insert_func() returns trigger AS

omm-# $$

omm$# DECLARE

omm$# BEGIN

omm$# insert into target_table values(new.id);

omm$# return new;

omm$# end

omm$# $$ language plpgsql;

CREATE FUNCTION

omm=# 



omm=# create trigger insert_trigger

omm-# before insert on source_table

omm-# for each ROW

omm-# execute PROCEDURE tri_insert_func();

CREATE TRIGGER

2.在源表上执行insert操作，查看触发操作是否生效；禁用触发器后，再次查看触发操作是否生效

omm=# insert into source_table values(1),(2),(3);

INSERT 0 3

omm=# select * from source_table;

 id 

----

  1

  2

  3

(3 rows)

omm=# select * from target_table;

 id 

----

  1

  2

  3

(3 rows)

omm=# 



omm=# alter table source_table disable trigger insert_trigger;

ALTER TABLE

omm=# insert into source_table values (4),(5),(6);

INSERT 0 3

omm=# 

omm=# select * from source_table;

 id 

----

  1

  2

  3

  4

  5

  6

(6 rows)

omm=# select * from target_table;

 id 

----

  1

  2

  3

(3 rows)

3.使用系统表PG_TRIGGER和\dS+查看触发器

omm=# select * from pg_trigger;

 tgrelid |     tgname     | tgfoid | tgtype | tgenabled | tgisinternal | tgconstrrelid | tgconstrindid | tgconstraint 

| tgdeferrable | tginitdeferred | tgnargs | tgattr | tgargs | tgqual | tgowner 

---------+----------------+--------+--------+-----------+--------------+---------------+---------------+--------------

+--------------+----------------+---------+--------+--------+--------+---------

   16398 | insert_trigger |  16404 |      7 | D         | f            |             0 |             0 |            0 

| f            | f              |       0 |        | \x     |        |      10

   16413 | insert_trigger |  16404 |      7 | D         | f            |             0 |             0 |            0 

| f            | f              |       0 |        | \x     |        |      10

(2 rows)

omm=# 



omm=# \dS+ source_table

                     Table "public.source_table"

 Column |  Type   | Modifiers | Storage | Stats target | Description 

--------+---------+-----------+---------+--------------+-------------

 id     | integer |           | plain   |              | 

Disabled triggers:

    insert_trigger BEFORE INSERT ON source_table FOR EACH ROW EXECUTE PROCEDURE tri_insert_func()

Has OIDs: no

Options: orientation=row, compression=no

4.重命名触发器

omm=# ALTER TRIGGER insert_trigger ON source_table RENAME TO insert_trigger_new;

ALTER TRIGGER

omm=# \dS+ source_table

                     Table "public.source_table"

 Column |  Type   | Modifiers | Storage | Stats target | Description 

--------+---------+-----------+---------+--------------+-------------

 id     | integer |           | plain   |              | 

Disabled triggers:

    insert_trigger_new BEFORE INSERT ON source_table FOR EACH ROW EXECUTE PROCEDURE tri_insert_func()

Has OIDs: no

Options: orientation=row, compression=no

5.删除触发器

omm=# drop trigger insert_trigger_new on source_table;

DROP TRIGGER