SQL入門(5)——表的設計、主鍵、外來鍵
阿新 • • 發佈：2019-02-14
定義主鍵約束（每一個表必須有一個主鍵列）
create table student
(
id int primary key,
name varchar(40)
);
定義主鍵自動增長
create table student
(
id int primary key auto_increment,
name varchar(40)
);
定義唯一約束
drop table student;
create table student
(
id int primary key auto_increment,
name varchar(40) unique
);
定義非空約束
drop table student;
create table student
(
id int primary key auto_increment,
name varchar(40) unique not null
);
定義外來鍵約束
create table husband
(
id int primary key,
name varchar(40)
);
create table wife
(
id int primary key,
name varchar(40),
husband_id int,
constraint husband_id_FK foreign key(husband_id) references husband(id)
);
一對多或多對一的物件存到資料庫時，表的設計方案
部門和員工
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)
);
多對多物件的表的設計（老師和學生）
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)
);
一對一的物件的資料庫設計
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)
);
自連線的表
create table person
(
id int primary key,
name varchar(40),
parent_id int,
constraint parent_id_FK foreign key(parent_id) references person(id)
);
create table student
(
id int primary key,
name varchar(40)
);
定義主鍵自動增長
create table student
(
id int primary key auto_increment,
name varchar(40)
);
定義唯一約束
drop table student;
create table student
(
id int primary key auto_increment,
name varchar(40) unique
);
定義非空約束
drop table student;
create table student
(
id int primary key auto_increment,
name varchar(40) unique not null
);
定義外來鍵約束
create table husband
(
id int primary key,
name varchar(40)
);
create table wife
(
id int primary key,
name varchar(40),
husband_id int,
constraint husband_id_FK foreign key(husband_id) references husband(id)
);
一對多或多對一的物件存到資料庫時，表的設計方案
部門和員工
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)
);
多對多物件的表的設計（老師和學生）
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)
);
一對一的物件的資料庫設計
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)
);
自連線的表
create table person
(
id int primary key,
name varchar(40),
parent_id int,
constraint parent_id_FK foreign key(parent_id) references person(id)
);