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数据库项目实战五

news 2025/11/13 5:40:52

一、项目内容

二、项目过程

2.1 创建两张表：

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)

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)

2.2 在商品表中导入商品记录

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

2.3 创建三种触发器

（1）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

mysql> create trigger orders_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 (0.01 sec)

mysql> insert into orders(gid,name,price,onum,otime) value('A0001','橡
皮',2.50,20,now());
Query OK, 1 row affected, 1 warning (0.01 sec)

mysql> select * from orders;
+-----+-------+--------+-------+------+------------+
| oid | gid | name | price | onum | otime |
+-----+-------+--------+-------+------+------------+
| 1 | A0001 | 橡皮 | 2.50 | 20 | 2025-11-12 |
+-----+-------+--------+-------+------+------------+
1 row in set (0.00 sec)

（2）更新型触发器的实现功能:客户取消订单，恢复商品表对应商品的数量

mysql> create trigger ordedrs_after_update_trigger
-> after update on orders for each row
-> update goods set num=num+(old.onum-new.onum);
Query OK, 0 rows affected (0.00 sec)

mysql> update orders set onum=40 where oid=1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0

（3）删除订单触发器的实现功能:客户修改订单，商品表对应商品数量同步更新

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;
Query OK, 0 rows affected (0.01 sec)

mysql> delete from orders where oid=1;
Query OK, 1 row affected (0.00 sec)

结果：

mysql> select * from goods;
+-------+-----------+-------+------+
| gid | name | price | num |
+-------+-----------+-------+------+
| A0001 | 橡皮 | 2.50 | 100 |
| B0001 | 小楷本 | 2.80 | 190 |
| C0001 | 铅笔 | 1.20 | 100 |
| D0001 | 计算器 | 28.00 | 0 |
+-------+-----------+-------+------+
4 rows in set (0.00 sec)

2.4 存储过程

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)

（1）创建提取emp_new表所有员工姓名和工资的存储过程s1

（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 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 ;
mysql> call s2('张三',@age);
Query OK, 1 row 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 in_dept int , out avg_sal float)
-> begin
-> select round(avg(incoming),2) into avg_sal from emp_new where dept2=in_dept;
-> end //
Query OK, 0 rows affected (0.01 sec)

mysql> delimiter ;
mysql> call s3(101,@sal);
Query OK, 1 row affected (0.00 sec)