MySQL触发器和存储过程

1、触发器

（1）：建立触发器，订单表中增加订单数量后，商品表商品数量同步减少对应的商品订单出数量,并测试

sql 复制代码

mysql> create trigger orders_after_insert_trigger
    -> after insert on orders for each row
    -> update goods set num=new-new.onum
    -> where gid=new.gid;
Query OK, 0 rows affected (0.01 sec)
mysql>

购买80根铅笔并观察表的数量是否减少

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mysql> insert into orders(gid,name,price,onum,otime) value('C0001','铅笔',1.20,80,now());
mysql> select * from goods;
gid  name     price  num
A0001  橡皮     2.50  100
B0001  小楷本   2.80  210
C0001  铅笔     1.20  120
D0001  计算器   28.00  20
4 rows in set (0.01 sec)
mysql> insert into orders (gid, name, price, onum, otime) value('C0001', '铅笔', 1. 20, 80, now());
Query OK, 1 row affected, 1 warning (0.01 sec)
mysql> select * from goods;
gid  name     price  num
A0001  橡皮     2.50  100
B0001  小楷本   2.80  210
C0001  铅笔     1.20  40
D0001  计算器   28.00  20
4 rows in set (0.00 sec)

（2）：建立触发器，实现功能:客户取消订单，恢复商品表对应商品的数量

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mysql> create trigger orders_after_delete_trigger
    -> after delete on orders for each row
    -> update goods set num=num+old.onum
    -> where gid=old.gid;

取消订单

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mysql> delete from orders where gid='C0001';

（3）：建立触发器，实现功能:客户修改订单，商品表对应商品数量同步更新

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mysql> create trigger orders_after_update_trigger
    -> after update on orders for each row
    -> update goods set num=num+(old,onum-new.onum)
    -> where gid=old.gid;
mysql> insert into orders(gid, name, price, onum, otime) value('A0001','橡皮', 2.5, 50, now());
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> select * from orders;
oid | gid | name | price | onum | otime
2 | A0001 | 橡皮 | 2.50 | 50 | 2024-07-26
1 row in set (0.00 sec)
mysql> select * from goods;
gid | name | price | num
A0001 | 橡皮 | 2.50 | 50
B0001 | 小楷本 | 2.80 | 210
C0001 | 铅笔 | 1.20 | 120
D0001 | 计算器 | 28.00 | 20
4 rows in set (0.00 sec)

2、存储过程

（1）：使用mydb7 openlab库

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mysql>  use mydb7_openlab;
Database changed

（2）：创建提取emp_new表所有员工姓名和工资的存储过程s1

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mysql> delimiter //
mysql> create procedure sl()
-> begin
-> select name, incoming from emp_new;
-> end //
Query OK, 0 rows affected (0.01 sec)
mysql> delimiter ;

使用命令查看员工姓名和工资

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mysql> call sl();
+-------+----------+
| name | incoming |
+-------+----------+
| 张三 | 4000 |
| 李四 | 3500 |
| 王五 | 2000 |
| 赵六 | 7500 |
| 荣七 | 8500 |
| 牛八 | 7300 |
+-------+----------+
6 rows in set (0.01 sec)
Query OK, 0 rows affected (0.01 sec)

（3）：创建存储过程s2，实现输入员工姓名后返回员工的年龄

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mysql> desc emp_new;
Field	Type	Null	Key	Default	Extra
---+
+
sid	int	YES		NULL
name	varchar(11)	YES		NULL
age	int	YES		NULL
worktime_start	date	YES		NULL
incoming	int	YES		NULL
dept2	int	YES		NULL
+
-----+
6 rows in set (0.01 sec)

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mysql> delimiter //
mysql> create procedure s2(in in_name varchar(11), out out_age int)
-> begin
-> select age into out_age from emp_new where name=in_name;
-> end //
Query OK, 0 rows affected (0.01 sec)
mysql> delimiter ;

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mysql> call s2('王五',@age);
mysql> select @age;
+------+
| @age |
+------+
| 24    |
+------+
1 row in set (0.01 sec)

（4）：创建一个存储过程s3，有2个参数，传入部门号，返回该部门的平均工资

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mysql> desc emp_new;
------+------+------+------+----------+-------
Field | Type | Null | Key | Default | Extra
------+------+------+------+----------+-------
sid | int | YES |  | NULL | 
name | varchar(11) | YES |  | NULL | 
age | int | YES |  | NULL | 
worktime_start | date | YES |  | NULL | 
incoming | int | YES |  | NULL | 
dept2 | int | YES |  | NULL | 
------+------+------+------+----------+-------
6 rows in set (0.00 sec)
mysql> delimiter //
mysql> create procedure s3(in in_dept int, out avg_sal float)
-> begin
-> select avg(incoming) into avg_sal from emp_new where dept2=in_dept;
-> end //
Query OK, 0 rows affected (0.01 sec)
mysql> delimiter;

使用s3

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mysql> call s3(102,@avg_sal);
mysql> select @avg_sal;
+-
-+
| @avg_sal |
----+
8000
1 row in set (0.00 sec)