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;