mysql创建表

说明:此文件包含了blog数据库中建立所有的表的Mysql语句.

在sql语句中注意“约束的概念":
1.实体完整性约束(主键--唯一且非空) primary key()
违约处理:No action(拒绝执行)

2.参照完整性约束(外键约束)foregin key() references tableName(filedName) [on delete|update casecade | no action]
违约处理:级联更新或拒绝执行

3.用户自定义完整性约束(not null,unique,check短语)
违约处理:拒绝执行

//添加列语法
//【alter table blog_article add columName type constraint】
//添加约束例子
//【alter table blog_article add CONSTRAINT foreign key(category_Name) references blog_category(category_Name) on delete cascade on update cascade】

问题:如何让相册，相片，文章公用一个评论表?

create database blog;

create table blog_user
(
user_Name char(15) not null check(user_Name !=''),
user_Password char(15) not null,
user_emial varchar(20) not null unique,
primary key(user_Name)

)engine=innodb default charset=utf8 auto_increment=1;

create table blog_category
(
category_Name char(18) not null check(category_Name!=''),
category_Date datetime not null,
primary key(category_Name)
)engine=innod default charset=utf8 auto_increment=1;

create table blog_article
(
article_Id int unsigned not null  auto_increment,
article_title varchar(20) not null unique,
article_content longtext not null,
article_date datetime not null,
article_readTime int unsigned not null default 0,
user_Name char(15) not null,
category_Name char(18) not null,
primary key(article_Id),
foreign key(user_Name) references blog_user(user_Name) on delete cascade on update cascade,
foreign key(category_Name) references blog_category(category_Name) on delete cascade on update cascade
)engine=innodb default charset=utf8 auto_increment=1;

CREATE TABLE blog_comment (
comment_Id int(10) unsigned NOT NULL AUTO_INCREMENT,
comment_Content varchar(90) NOT NULL,
comment_Date datetime NOT NULL,
article_Id int(10) unsigned NOT NULL,
user_Name char(15) NOT NULL,
PRIMARY KEY (comment_Id),
foreign key(article_Id) references blog_article(article_Id) on delete cascade on update cascade,
foreign key(user_Name) references blog_user(user_Name) on delete cascade on update cascade
)engine=innodb default charset=utf8 auto_increment=1;

create table blog_photoAlbum
(
photoAlbum_Name char(20) not null check(photoAlbum_Name!=''),
photoAlbum_Date datetime not null,
primary key(photoAlbum_Name)
)engine=innodb default charset=utf8;

create table blog_photograph
(
photograph_Name varchar(20) not null check(photograph_Name!=''),
photograph_Date datetime not null,
photoAlbum_Name char(20)  not null,
photoURL varchar(90) not null,
foreign key(photoAlbum_Name) references blog_photoAlbum(photoAlbum_Name) on delete cascade on update cascade
)engine=innodb default charset=utf8;