MySQL触发器

创建表并导入数据；

mysql> use mydb16_trigger;
Database changed
mysql> create table goods(
    -> gid char(8) primary key,
    -> name varchar(10),
    -> price decimal(8,2),
    -> num int
    -> );
Query OK, 0 rows affected (0.07 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)

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

创建触发器：订单表中增加订单数量时，商品表商品数量同步减少对应的商品订单数量；

mysql> delimiter //
mysql> create trigger before_order_insert
    -> before insert on orders
    -> for each row
    -> begin
    ->      update goods
    ->      set num =num - new.onum
    ->      where gid = new.gid;
    -> end //
Query OK, 0 rows affected (0.05 sec)

mysql> delimiter ;
mysql> insert into orders (gid, name, price, onum, otime) values ('A0001', '橡皮', 2.5, 10, '2025-02-09');
Query OK, 0 rows affected (0.04 sec)

创建触发器：客户取消订单，恢复商品对应商品的数量;

mysql> delimiter //
mysql> create trigger after_order_delete
    -> after delete on orders
    -> for each row
    -> begin
    ->     update goods
    ->     set num = num + old.onum
    ->     where gid = old.gid;
    -> end //
Query OK, 0 rows affected (0.04 sec)

mysql> delimiter ;
mysql> delete from orders where oid = 1;
Query OK, 0 rows affected (0.04 sec)

创建触发器：客户修改订单，商品对应商品数量同步更新;

mysql> delimiter //
mysql> create trigger after_order_update
    -> after update on orders
    -> for each row
    -> begin
    ->     update goods
    ->     set num = num - new.onum + old.onum
    ->     where gid = new.gid;
    -> end //
Query OK, 0 rows affected (0.04 sec)

mysql> delimiter ;
mysql> update orders set onum = 5 where oid = 1;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 0  Changed: 0  Warnings: 0

创建提取emp_new表所有员工姓名和工资的存储过程s1

mysql> use mydb7_openlab;
Database changed
mysql> delimiter //
mysql> create procedure s1()
    -> begin
    ->     select 员工姓名, 工资
    ->     from emp_new;
    -> end //
Query OK, 0 rows affected (0.04 sec)

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), out emp_age int)
    -> begin
    ->     select 年龄 into emp_age
    ->     from emp_new
    ->     where 员工姓名 = emp_name;
    -> end //
Query OK, 0 rows affected (0.04 sec)

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_no int, out avg_salary decimal(10,2))
    -> begin
    ->     select avg(工资) into avg_salary
    ->     from emp_new
    ->     where 部门号 = dept_no;
    -> end //
Query OK, 0 rows affected (0.04 sec)

MySQL触发器

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