MySQL-20.多表设计-一对一多对多

一.一对一

在数据的一对一关系中，可以在任意一个数据表中添加对另一个表的外键约束，但是该外键约束必须是unique的，否则无法实现一对一关系。

create table tb_user(
                        id int unsigned  primary key auto_increment comment 'ID',
                        name varchar(10) not null comment '姓名',
                        gender tinyint unsigned not null comment '性别, 1 男  2 女',
                        phone char(11) comment '手机号',
                        degree varchar(10) comment '学历'
) comment '用户信息表';

insert into tb_user values (1,'白眉鹰王',1,'18812340001','初中'),
                           (2,'青翼蝠王',1,'18812340002','大专'),
                           (3,'金毛狮王',1,'18812340003','初中'),
                           (4,'紫衫龙王',2,'18812340004','硕士');


create table tb_user_card(
                             id int unsigned  primary key auto_increment comment 'ID',
                             nationality varchar(10) not null comment '民族',
                             birthday date not null comment '生日',
                             idcard char(18) not null comment '身份证号',
                             issued varchar(20) not null comment '签发机关',
                             expire_begin date not null comment '有效期限-开始',
                             expire_end date comment '有效期限-结束',
                             user_id int unsigned not null unique comment '用户ID',
                             constraint fk_user_id foreign key (user_id) references tb_user(id)
) comment '用户信息表';

insert into tb_user_card values (1,'汉','1960-11-06','100000100000100001','朝阳区公安局','2000-06-10',null,1),
                                (2,'汉','1971-11-06','100000100000100002','静安区公安局','2005-06-10','2025-06-10',2),
                                (3,'汉','1963-11-06','100000100000100003','昌平区公安局','2006-06-10',null,3),
                                (4,'回','1980-11-06','100000100000100004','海淀区公安局','2008-06-10','2028-06-10',4);

 二.多对多

create table tb_student(
                           id int auto_increment primary key comment '主键ID',
                           name varchar(10) comment '姓名',
                           no varchar(10) comment '学号'
) comment '学生表';
insert into tb_student(name, no) values ('黛绮丝', '2000100101'),('谢逊', '2000100102'),('殷天正', '2000100103'),('韦一笑', '2000100104');


create table tb_course(
                          id int auto_increment primary key comment '主键ID',
                          name varchar(10) comment '课程名称'
) comment '课程表';
insert into tb_course (name) values ('Java'), ('PHP'), ('MySQL') , ('Hadoop');


create table tb_student_course(
                                  id int auto_increment comment '主键' primary key,
                                  student_id int not null comment '学生ID',
                                  course_id  int not null comment '课程ID',
                                  constraint fk_courseid foreign key (course_id) references tb_course (id),
                                  constraint fk_studentid foreign key (student_id) references tb_student (id)
)comment '学生课程中间表';

insert into tb_student_course(student_id, course_id) values (1,1),(1,2),(1,3),(2,2),(2,3),(3,4);