# 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

#准备表
CREATE TABLE cmd (
    id INT PRIMARY KEY auto_increment,
    USER CHAR (32),
    priv CHAR (10),
    cmd CHAR (64),
    sub_time datetime, #提交时间
    success enum ('yes', 'no') #0代表执行失败
);

CREATE TABLE errlog (
    id INT PRIMARY KEY auto_increment,
    err_cmd CHAR (64),
    err_time datetime
);

#创建触发器
delimiter //
CREATE TRIGGER tri_after_insert_cmd AFTER INSERT ON cmd FOR EACH ROW
BEGIN
    IF NEW.success = 'no' THEN #等值判断只有一个等号
            INSERT INTO errlog(err_cmd, err_time) VALUES(NEW.cmd, NEW.sub_time) ; #必须加分号
      END IF ; #必须加分号
END//
delimiter ;


#往表cmd中插入记录，触发触发器，根据IF的条件决定是否插入错误日志
INSERT INTO cmd (
    USER,
    priv,
    cmd,
    sub_time,
    success
)
VALUES
    ('A','0755','ls -l /etc',NOW(),'yes'),
    ('A','0755','cat /etc/passwd',NOW(),'no'),
    ('A','0755','useradd xxx',NOW(),'no'),
    ('A','0755','ps aux',NOW(),'yes');


#查询错误日志，发现有两条
mysql> select * from errlog;
+----+-----------------+---------------------+
| id | err_cmd         | err_time            |
+----+-----------------+---------------------+
|  1 | cat /etc/passwd | 2018-09-18 20:18:48 |
|  2 | useradd xxx     | 2018-09-18 20:18:48 |
+----+-----------------+---------------------+
2 rows in set (0.00 sec)

         案例:创建一个存储过程 作用是将两个整数相加
            create procedure add_p (in a int,in b int)
            begin
                select a + b;
            end

            //
      调用 call add_p(1,2)

         案例:创建一个存储过程 作用是将两个整数相加 将结果保存在变量中
        定义一个变量
        set @su = 100;
            create procedure add_p2 (in a int,in b int,out su int)
            begin
                set su = a + b;
            end

            //
    
    定义变量 set @su = 100;
    调用过程 call  add_p2(10,20,@su);

          注意  在存储过程中 需要使用分号来结束一行 但是分号有特殊含义
          得将原始的结束符 修改为其他符号
            delimiter // 结束符更换为//
            delimiter;

    create procedure show_p (in a int)
    begin
    if a = 1 then
        select "壹";
    elseif a = 2 then
        select "贰";
    else
        select "other";
    end if;
    end //

delimiter //
CREATE PROCEDURE proc_if ()
BEGIN
    
    declare i int default 0;
    if i = 1 THEN
        SELECT 1;
    ELSEIF i = 2 THEN
        SELECT 2;
    ELSE
        SELECT 7;
    END IF;

END //
delimiter ;

delimiter //
CREATE PROCEDURE proc_while ()
BEGIN

    DECLARE num INT ;
    SET num = 0 ;
    WHILE num < 10 DO
        SELECT
            num ;
        SET num = num + 1 ;
    END WHILE ;

END //
delimiter ;

delimiter //
CREATE PROCEDURE proc_repeat ()
BEGIN

    DECLARE i INT ;
    SET i = 0 ;
    repeat
        select i;
        set i = i + 1;
        until i >= 5
    end repeat;

END //
delimiter ;

BEGIN
    
    declare i int default 0;
    loop_label: loop
        
        set i=i+1;
        if i<8 then
            iterate loop_label;
        end if;
        if i>=10 then
            leave loop_label;
        end if;
        select i;
    end loop loop_label;

END