觸發器:對表進行增刪改操作之後,完成某操作,被稱之為觸發器

1.創建基本語法

 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 # 插入後
 8 CREATE TRIGGER tri_after_insert_tb1 AFTER INSERT ON tb1 FOR EACH ROW
 9 BEGIN
10     ...
11 END
12 
13 # 刪除前
14 CREATE TRIGGER tri_before_delete_tb1 BEFORE DELETE
 
 ON tb1 FOR EACH ROW
15 BEGIN
16     ...
17 END
18 
19 # 刪除後
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 # 更新後
32 CREATE TRIGGER
 
 tri_after_update_tb1 AFTER UPDATE ON tb1 FOR EACH ROW
33 BEGIN
34     ...
35 END

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 ;

 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 ;

特別的：NEW表示即將插入的數據行，OLD表示即將刪除的數據行。

2.刪除觸發器

DROP TRIGGER tri_after_insert_tb1;

3.使用觸發器:一旦對已經生成觸發器的數據表進行觸發條件操作,就會執行觸發器了

insert into tb1(num) values(666)

MySQL-觸發器