MySQL數據庫表的設計

表的約束

主鍵約束

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

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

 

惟一約束

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

nique);

 

非空約束

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

nique not null);

 

外鍵約束

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));

 

數據庫的設計

一對一（通常有主從關係，把從的那個表的主鍵做外鍵約束）

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));

 

一對多或多對一（先設計表，在多的一方加外鍵）

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));

 

多對多（先設計兩個表，再設計中間表(能夠設聯合主鍵)）

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));

 

自鏈接

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