多表查询的练习

土豆烧牛肉2019-06-05 11:05:15

用户表(user)

create table `user` (

`id` int auto_increment primary key,

`username` varchar(50) -- 用户姓名

);

-- 订单表(orders)

create table `orders` (

`id` int auto_increment primary key,

`price` double,

`user_id` int

);

-- 给订单表添加外键约束

alter table orders add constraint user_fk foreign key (user_id) references user(id);

-- 向user表中添加数据

insert into user values(3,'张三');

insert into user values(4,'李四');

insert into user values(5,'王五');

insert into user values(6,'赵六');

-- 向orders 表中插入数据

insert into orders values(1,1314,3);

insert into orders values(2,1314,3);

insert into orders values(3,15,4);

insert into orders values(4,315,5);

insert into orders values(5,1014,null);

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作者：如晴天-似雨天

来源：CSDN

原文：https://blog.csdn.net/puyu9714/article/details/82872984