18.1 打卡第18天
w👉openGauss SQL学习参考资料
https://opengauss.org/zh/docs/2.1.0/docs/Developerguide/SQL%E8%AF%AD%E6%B3%95.html
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
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
create table a1 (id int,score int);
create table a2 (id int,score int);
create or replace function tri_insert_func() returns trigger as
declare
begin
insert into a2 values (new.id,new.score);omm$#
return new;
end
$$ language plpgsql;
create trigger insert_trigger
before insert on a1
for each row
execute procedure tri_insert_func();
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
insert into a1 values (1,100);
alter table a1 disable trigger insert_trigger;
insert into a1 values (2,99);
select * from a1;
select * from a2;
3.使用系统表PG_TRIGGER和\dS+查看触发器
select * from pg_trigger;
\ds+ a1;
4.重命名触发器
alter trigger insert_trigger on a1 rename to insert_trigger2;
5.删除触发器
drop trigger insert_trigger2 on a1;
