MySQL数据库表的设计

表的约束

主键约束

create table student(id int primary key,name varchar(40));

create table student(id int primary key auto_increment,name varchar(20));

 

惟一约束

create table student(id int primary key auto_increment,name varchar(20) u

nique);

 

非空约束

create table student(id int primary key auto_increment,name varchar(20) u

nique not null);

 

外键约束

create table teacher(id int primary key auto_increment,name varchar(20) no

t null,student_id int,constraint student_id_FK foreign key(student_id) reference

s student(id));

 

数据库的设计

一对一（通常有主从关系，把从的那个表的主键做外键约束）

create table person(id int primary key,name varchar(40));

create table idcard(id int primary key,city varchar(40),constraint id_FK foreign key(id) references person(id));

 

一对多或多对一（先设计表，在多的一方加外键）

create table department(id int primary key,name varchar(40));

create table employee(id int primary key,name varchar(40),salary decimal(8,2),department_id int,constraint department_id_FK foreign key(department_id) references department(id));

 

多对多（先设计两个表，再设计中间表(能够设联合主键)）

create table teacher(id int primary key,name varchar(40),salary decimal(8,2));

create table student(id int primary key,name varchar(40));

create table teacher_student

(teacher_id int,student_id int,primary key(teacher_id,student_id),constraint teacher_id_FK foreign key(teacher_id) references teacher(id),constraint student_id_FK foreign key(student_id) references student(id));

 

自链接

create table person(id int primary key,name varchar(40),parent_id int,constraint parent_id_FK foreign key(parent_id) references person(id));