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;