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

# 插入前
CREATE TRIGGER tri_before_insert_tb1 BEFORE INSERT ON tb1 FOR EACH ROW
BEGIN
    ...
END

# 插入后
CREATE TRIGGER tri_after_insert_tb1 AFTER INSERT ON tb1 FOR EACH ROW
BEGIN
    ...
END

# 删除前
CREATE TRIGGER tri_before_delete_tb1 BEFORE DELETE ON tb1 FOR EACH ROW
BEGIN
    ...
END

# 删除后
CREATE TRIGGER tri_after_delete_tb1 AFTER DELETE ON tb1 FOR EACH ROW
BEGIN
    ...
END

# 更新前
CREATE TRIGGER tri_before_update_tb1 BEFORE UPDATE ON tb1 FOR EACH ROW
BEGIN
    ...
END

# 更新后
CREATE TRIGGER tri_after_update_tb1 AFTER UPDATE ON tb1 FOR EACH ROW
BEGIN
    ...
END

delimiter //
CREATE TRIGGER tri_before_insert_tb1 BEFORE INSERT ON tb1 FOR EACH ROW
BEGIN
IF NEW. NAME == 'alex' THEN
    INSERT INTO tb2 (NAME)
VALUES
    ('aa')
END//
delimiter ;

delimiter //
CREATE TRIGGER tri_after_insert_tb1 AFTER INSERT ON tb1 FOR EACH ROW
BEGIN
    IF NEW. num = 666 THEN
        INSERT INTO tb2 (NAME)
        VALUES
            ('666'),
            ('666') ;
    ELSEIF NEW. num = 555 THEN
        INSERT INTO tb2 (NAME)
        VALUES
            ('555'),
            ('555') ;
    END IF;
END//
delimiter ;

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)