MySQL练习五 触发器和存储过程
作业
1、触发器
建立两个表：goods(商品表)、orders(订单表)
在商品表中导入商品记录
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
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
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
建表
mysql> use mydb16_trigger;
Database changed
# 创建商品表
mysql> create table goods(
-> gid char(8) primary key,
-> name varchar(10),
-> price decimal(8,2),
-> num int
-> );
Query OK, 0 rows affected (0.02 sec)
# 创建订单表
mysql> create table orders(
-> oid int primary key auto_increment,
-> gid char(10) not null,
-> name varchar(10),
-> price decimal(8,2),
-> onum int,
-> otime date
-> );
Query OK, 0 rows affected (0.02 sec)
# 插入记录
mysql> insert into goods values
-> ('A0001','橡皮',2.5,100),
-> ('B0001','小楷本',2.8,210),
-> ('C0001','铅笔',1.2,120),
-> ('D0001','计算器',28,20);
Query OK, 4 rows affected (0.01 sec)
Records: 4 Duplicates: 0 Warnings: 0
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)增加订单
# 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
mysql> create trigger after_insert_trigger
-> after insert on orders for each row
-> update goods set num = num - new.onum
-> where gid = new.gid;
Query OK, 0 rows affected (0.00 sec)
# 插入一个订单
mysql> insert into orders(gid, name, price, onum, otime) values('A0001','订单1',2.5,3,now());
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> select * from orders;
+-----+-------+---------+-------+------+------------+
| oid | gid | name | price | onum | otime |
+-----+-------+---------+-------+------+------------+
| 1 | A0001 | 订单1 | 2.50 | 3 | 2025-02-08 |
+-----+-------+---------+-------+------+------------+
1 row in set (0.00 sec)
# 查表发现橡皮数量同步减少
mysql> select * from goods;
+-------+-----------+-------+------+
| gid | name | price | num |
+-------+-----------+-------+------+
| A0001 | 橡皮 | 2.50 | 97 |
| 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)删除订单
# 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
mysql> create trigger before_delete_trigger
-> before delete on orders for each row
-> update goods set num = num + old.onum
-> where gid = old.gid;
Query OK, 0 rows affected (0.01 sec)
# 删除1号订单后发现商品数量还原
mysql> delete from orders where oid = 1;
Query OK, 1 row affected (0.00 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 | 120 |
| D0001 | 计算器 | 28.00 | 20 |
+-------+-----------+-------+------+
4 rows in set (0.00 sec)更新订单
# 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
mysql> delimiter //
# 分为新订单数量相比之前增加和减少两种情况
mysql> create trigger after_update_trigger
-> after update on orders for each row
-> begin
-> if new.onum > old.onum then
-> update goods set num = num - (new.onum - old.onum)
where gid = new.gid;
-> elseif new.onum < old.onum then
-> update goods set num = num + (old.onum - new.onum)
where gid = new.gid;
-> end if;
-> end //
Query OK, 0 rows affected (0.01 sec)
mysql> delimiter ;
# 重新添加订单
mysql> insert into orders(gid, name, price, onum, otime) values('A0001','订单1',2.5,3,now());
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> select * from orders;
+-----+-------+---------+-------+------+------------+
| oid | gid | name | price | onum | otime |
+-----+-------+---------+-------+------+------------+
| 2 | A0001 | 订单1 | 2.50 | 3 | 2025-02-08 |
+-----+-------+---------+-------+------+------------+
1 row in set (0.00 sec)
# 将订单数更新为 5 份
mysql> update orders set onum = 5 where oid = 2;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 0 Changed: 0 Warnings: 0
mysql> select * from goods;
+-------+-----------+-------+------+
| gid | name | price | num |
+-------+-----------+-------+------+
| A0001 | 橡皮 | 2.50 | 95 |
| 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)
mysql> select * from orders;
+-----+-------+---------+-------+------+------------+
| oid | gid | name | price | onum | otime |
+-----+-------+---------+-------+------+------------+
| 2 | A0001 | 订单1 | 2.50 | 5 | 2025-02-08 |
+-----+-------+---------+-------+------+------------+
1 row in set (0.00 sec)
# 减少同理
mysql> update orders set onum = 1 where oid = 2;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from goods;
+-------+-----------+-------+------+
| gid | name | price | num |
+-------+-----------+-------+------+
| A0001 | 橡皮 | 2.50 | 99 |
| 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)
mysql> select * from orders;
+-----+-------+---------+-------+------+------------+
| oid | gid | name | price | onum | otime |
+-----+-------+---------+-------+------+------------+
| 2 | A0001 | 订单1 | 2.50 | 1 | 2025-02-08 |
+-----+-------+---------+-------+------+------------+
1 row in set (0.00 sec)2、存储过程
使用mydb7_openlab库
创建提取emp_new表所有员工姓名和工资的存储过程 s1
创建存储过程 s2，实现输入员工姓名后返回员工的年龄
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
员工表展示
mysql> use mydb7_openlab;
Database changed
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> select * from emp_new;
+------+--------+------+----------------+----------+-------+
| sid | name | age | worktime_start | incoming | dept2 |
+------+--------+------+----------------+----------+-------+
| 1789 | 张三 | 35 | 1980-01-01 | 4000 | 101 |
| 1674 | 李四 | 32 | 1983-04-01 | 3500 | 101 |
| 1776 | 王五 | 24 | 1990-07-01 | 2000 | 101 |
| 1568 | 赵六 | 57 | 1970-10-11 | 7500 | 102 |
| 1564 | 荣七 | 64 | 1963-10-11 | 8500 | 102 |
| 1879 | 牛八 | 55 | 1971-10-20 | 7300 | 103 |
+------+--------+------+----------------+----------+-------+
6 rows in set (0.00 sec)存储过程创建
### 1. 创建提取emp_new表所有员工姓名和工资的存储过程 s1
mysql> delimiter //
mysql> create procedure s1()
-> begin
-> select name, incoming from emp_new;
-> end //
Query OK, 0 rows affected (0.01 sec)
mysql> delimiter ;
mysql> call s1();
+--------+----------+
| name | incoming |
+--------+----------+
| 张三 | 4000 |
| 李四 | 3500 |
| 王五 | 2000 |
| 赵六 | 7500 |
| 荣七 | 8500 |
| 牛八 | 7300 |
+--------+----------+
6 rows in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
### 2. 创建存储过程 s2，实现输入员工姓名后返回员工的年龄
mysql> delimiter //
mysql> create procedure s2(in emp_name varchar(50))
-> begin
-> select age from emp_new where name = emp_name;
-> end //
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;
# 这里查询李四的年龄
mysql> call s2('李四');
+------+
| age |
+------+
| 32 |
+------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
### 3. 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
mysql> delimiter //
mysql> create procedure s3(in dept_num int, out avg_income decimal(10,2))
-> begin
-> select avg(incoming) into avg_income from emp_new
-> where dept2 = dept_num;
-> end //
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;
# 初始化
mysql> set @avg_income = 0;
Query OK, 0 rows affected (0.00 sec)
# 这里我们查询101部门的平均工资
mysql> call s3(101, @avg_income);
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> select @avg_income;
+-------------+
| @avg_income |
+-------------+
| 3166.67 |
+-------------+
1 row in set (0.00 sec)