柚子快报激活码778899分享：MySQL-触发器
触发器:对表进行增删改操作之后,完成某操作,被称之为触发器
1.创建基本语法
1 # 插入前
2 CREATE TRIGGER tri_before_insert_tb1 BEFORE INSERT ON tb1 FOR EACH ROW
3 BEGIN
4 ...
5 END
6
7 # 插入后
8 CREATE TRIGGER tri_after_insert_tb1 AFTER INSERT ON tb1 FOR EACH ROW
9 BEGIN
10 ...
11 END
12
13 # 删除前
14 CREATE TRIGGER tri_before_delete_tb1 BEFORE DELETE ON tb1 FOR EACH ROW
15 BEGIN
16 ...
17 END
18
19 # 删除后
20 CREATE TRIGGER tri_after_delete_tb1 AFTER DELETE ON tb1 FOR EACH ROW
21 BEGIN
22 ...
23 END
24
25 # 更新前
26 CREATE TRIGGER tri_before_update_tb1 BEFORE UPDATE ON tb1 FOR EACH ROW
27 BEGIN
28 ...
29 END
30
31 # 更新后
32 CREATE TRIGGER tri_after_update_tb1 AFTER UPDATE ON tb1 FOR EACH ROW
33 BEGIN
34 ...
35 END
创建触发器
1 delimiter //
2 CREATE TRIGGER tri_before_insert_tb1 BEFORE INSERT ON tb1 FOR EACH ROW
3 BEGIN
4 IF NEW. NAME == 'alex' THEN
5 INSERT INTO tb2 (NAME)
6 VALUES
7 ('aa')
8 END//
9 delimiter ;
示例:insert之前
1 delimiter //
2 CREATE TRIGGER tri_after_insert_tb1 AFTER INSERT ON tb1 FOR EACH ROW
3 BEGIN
4 IF NEW. num = 666 THEN
5 INSERT INTO tb2 (NAME)
6 VALUES
7 ('666'),
8 ('666') ;
9 ELSEIF NEW. num = 555 THEN
10 INSERT INTO tb2 (NAME)
11 VALUES
12 ('555'),
13 ('555') ;
14 END IF;
15 END//
16 delimiter ;
示例:insert之后
特别的：NEW表示即将插入的数据行，OLD表示即将删除的数据行。
2.删除触发器
DROP TRIGGER tri_after_insert_tb1;
3.使用触发器:一旦对已经生成触发器的数据表进行触发条件操作,就会执行触发器了
insert into tb1(num) values(666)
柚子快报激活码778899分享：MySQL-触发器
发表评论