一、创建多对多1.学生表create table students ( id int not null primary key auto_increment, name varchar(45) not null )engine=innodb default charset=utf8;
2.课程表create table courses ( id int not null primary key auto_increment, name varchar(45) not null )engine=innodb default charset=utf8;
3.中间表create table stu_cour ( id int not null primary key auto_increment course_id int not null, stu_id int not null, constraint cour foreign key(course_id) references courses(id), constraint stu foreign key(stu_id) references students(id) )engine=innodb default charset=utf8;
4.插入数据insert into students values (0,"小王");insert into students values (0,"小宋");insert into students values (0,"小李");insert into courses values (0,"语文");insert into courses values (0,"数学");insert into courses values (0,"英语");insert into stu_cour values (0,1,1);insert into stu_cour values (0,1,2);insert into stu_cour values (0,1,3);insert into stu_cour values (0,2,1);insert into stu_cour values (0,2,3);insert into stu_cour values (0,3,2);insert into stu_cour values (0,3,3);
5.查询学生1选了哪些科目select courses.id,courses.name from courses inner join stu_cour on stu_cour.course_id=courses.idinner join students on students.id= 1 and students.id = stu_cour.stu_id;
6.查询id=2数学被谁选了select students.name from students inner join stu_cour on stu_cour.stu_id =students.idinner join courses on courses.id= 2 and stu_cour.course_id = courses.id;
二、mysql 创建一对一关系1.一对一创建用户表：
create table users (id int not null primary key auto_increment,name varchar(50) not null)engine=innodb default charset=utf8;
用户信息表：
create table users_info (id int not null primary key auto_increment,age int not null,phone varchar(11) not null,user_id int not null,constraint user_info foreign key(user_id) references users(id))engine=innodb default charset=utf8;
2.插入数据insert into users values (0,"小王");insert into users values (0,"小宋");insert into users_info values (0,12,'13812345678',1);insert into users_info values (0,14,'13812345679',2);
查询人的全部信息：
select * from users inner join users_info onusers_info.user_id =users.id;
以上就是mysql如何创建多对多和一对一关系的详细内容。