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MySQL第五次作业（触发器，存储过程）

news 2025/11/12 7:07:56

要求：

创建相应表：

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

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 ) ;
mysql> desc  orders;

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','计算器',28, 20);

1.触发器

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

create  trigger  orders_insert_after_trigger-> after  insert  on  orders-> for  each row-> update  goods  set  num=num-new.onum  where  gid = new.gid ;

 select * from goods;insert into orders(gid,name,price,onum,otime) values('A0001','橡皮',2.50,20,now());
select * from orders;select * from goods;

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  orders_delete_after_trigger-> after  delete  on  orders-> for  each row-> update  goods  set  num=num+old.onum  where  gid = old.gid ;
mysql> delete from orders where gid='A0001';
mysql>  select * from orders;
mysql>  select * from goods;

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> create  trigger  orders_update_after_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) values('A0001','橡皮',2.50,20,now());
mysql> select * from orders;
mysql> select * from goods;
mysql>  insert into orders(gid,name,price,onum,otime) values('A0001','橡皮',2.50,20,now());
mysql> select * from orders;
mysql> select * from goods;

mysql> insert into orders(gid,name,price,onum,otime) values('A0001','橡皮',2.50,30,now());
mysql>  select * from orders;
mysql> update orders set onum=20 where oid=4;
mysql> select * from orders;
mysql>  select * from goods;

2.存储过程：

使用 mydb7_openlab 库

use mydb7_openlab;

创建提取 emp_new 表所有员工姓名和工资的存储过程 s1

delimiter //
create procedure s1()
beginselect name, incoming from emp_new;
end //
delimiter ;
call s1();

创建存储过程 s2，实现输入员工姓名后返回员工的年龄

mysql> desc emp_new;
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  //
mysql> delimiter ;
mysql> call   s2('张三',@age);
mysql> select  @age;

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 out_sal decimal(10, 2))-> begin->     select round(avg(incoming), 2) into out_sal from emp_new where dept2 = in_dept;-> end //
mysql> delimiter ;
mysql> call s3(101,@sal);
mysql> select  @sal;