MySQL第五次作业

一、作业内容

一、触发器

建立表

mysql> use mydb16_trigger;

mysql> create table goods
    -> (
    ->          gid char(8) primary key,
    ->          name varchar(10),
    ->          price decimal(8,2),
    ->          num int
    -> );

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
    -> );

插入数据

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','计算计',28,20);

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

命令

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;

结果

插入数据前

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 | 计算计 | 28.00 |   20 |
+-------+--------+-------+------+

mysql> select * from orders;
Empty set (0.01 sec)

插入数据后

mysql> insert into orders(gid,name,price,onum,otime) value('B0001sql','小楷本',2.8,100,now());

mysql> select * from goods;
+-------+--------+-------+------+
| gid   | name   | price | num  |
+-------+--------+-------+------+
| A0001 | 橡皮   |  2.50 |  100 |
| B0001 | 小楷本 |  2.80 |  110 |
| C0001 | 铅笔   |  1.20 |  120 |
| D0001 | 计算计 | 28.00 |   20 |
+-------+--------+-------+------+

mysql> select * from orders;
+-----+-------+--------+-------+------+------------+
| oid | gid   | name   | price | onum | otime      |
+-----+-------+--------+-------+------+------------+
|   1 | B0001 | 小楷本 |  2.80 |  100 | 2024-07-25 |
+-----+-------+--------+-------+------+------------+

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

命令

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;

结果

取消前

mysql> select * from goods;
+-------+--------+-------+------+
| gid   | name   | price | num  |
+-------+--------+-------+------+
| A0001 | 橡皮   |  2.50 |  100 |
| B0001 | 小楷本 |  2.80 |  110 |
| C0001 | 铅笔   |  1.20 |  120 |
| D0001 | 计算计 | 28.00 |   20 |
+-------+--------+-------+------+

mysql> select * from orders;
+-----+-------+--------+-------+------+------------+
| oid | gid   | name   | price | onum | otime      |
+-----+-------+--------+-------+------+------------+
|   1 | B0001 | 小楷本 |  2.80 |  100 | 2024-07-25 |
+-----+-------+--------+-------+------+------------+

取消后

mysql> delete from orders where orders.oid=1;

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 | 计算计 | 28.00 |   20 |
+-------+--------+-------+------+
4 rows in set (0.00 sec)

mysql> select * from orders;
Empty set (0.00 sec)

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

命令

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;

结果

修改前

mysql> select * from goods;
+-------+--------+-------+------+
| gid   | name   | price | num  |
+-------+--------+-------+------+
| A0001 | 橡皮   |  2.50 |  100 |
| B0001 | 小楷本 |  2.80 |  110 |
| C0001 | 铅笔   |  1.20 |  120 |
| D0001 | 计算计 | 28.00 |   20 |
+-------+--------+-------+------+

mysql> select * from orders;
+-----+-------+--------+-------+------+------------+
| oid | gid   | name   | price | onum | otime      |
+-----+-------+--------+-------+------+------------+
|   1 | B0001 | 小楷本 |  2.80 |  100 | 2024-07-25 |
+-----+-------+--------+-------+------+------------+

修改后

mysql> update orders set onum=120 where gid='B0001';


mysql> select * from orders;
+-----+-------+--------+-------+------+------------+
| oid | gid   | name   | price | onum | otime      |
+-----+-------+--------+-------+------+------------+
|   2 | B0001 | 小楷本 |  2.80 |  120 | 2024-07-25 |
+-----+-------+--------+-------+------+------------+


mysql> select * from goods;
+-------+--------+-------+------+
| gid   | name   | price | num  |
+-------+--------+-------+------+
| A0001 | 橡皮   |  2.50 |  100 |
| B0001 | 小楷本 |  2.80 |   90 |
| C0001 | 铅笔   |  1.20 |  120 |
| D0001 | 计算计 | 28.00 |   20 |
+-------+--------+-------+------+

二、存储过程

1、使用mydb7 openlab库

mysql> use mydb7_openlab;

2、创建提取emp_new表所有员工姓名和工资的存储过程s1

命令

mysql> delimiter //
mysql> create procedure s1()
    -> begin
    ->          select name,incoming from emp_new;
    -> end //

结果

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 |
+------+----------+

3、创建存储过程s2，实现输入员工姓名后返回员工的年龄

命令

ysql> 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 //

结果

mysql> call s2('张三',@age);
Query OK, 1 row affected (0.00 sec)

mysql> select @age;
+------+
| @age |
+------+
|   35 |
+------+

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

命令

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 //

结果

mysql> call s3(102,@avg_sal);
Query OK, 1 row affected (0.00 sec)

mysql> select @avg_sal;
+----------+
| @avg_sal |
+----------+
|     8000 |
+----------+