MYSQL 新增字段 删除字段 修改字段 级联删除 级联更新

//添加字段并设置主键
ALTER TABLE tabelname ADD new_field_id int(5) unsigned default 0 not null auto_increment ,ADD primary key (new_field_id);

//加主关键字的索引
ALTER TABLE tablename ADD primary key(id);

//加索引
ALTER TABLE tablename CHANGE depno depno int(5) not null;
ALTER TABLE tablename ADD INDEX 索引名 (字段名1[，字段名2 …]);
ALTER TABLE tablename ADD INDEX emp_name (name);

//加唯一限制条件的索引
ALTER TABLE tablename ADD UNIQUE emp_name2(cardnumber);

//删除某个索引
ALTER TABLE tablename DROP INDEX emp_name;

//增加字段：
ALTER TABLE table_name ADD field_name field_type;

//删除字段
ALTER TABLE table_name DROP field_name;

//重命名列
ALTER TABLE table_name CHANGE field_name1 field_name2 integer;

//调整字段顺序
ALTER TABLE `users` CHANGE `user_password` `user_password` varchar( 20 ) NOT NULL AFTER user_name;

//改变列的类型
ALTER TABLE table_name CHANGE field_name field_name bigint not null;
ALTER TABLE infos CHANGE list list tinyint not null default '0';

//修改原字段名称及类型：
ALTER TABLE table_name CHANGE old_field_name new_field_name field_type;

//重命名表
ALTER TABLE table_name rename new_table_name;

//级联更新 和 删除
DROP TABLE IF EXISTS `mail_model`;create TABLE mail_model(id varchar(50) primary key not null ,mail_filename varchar(200),content varchar(2000))ENGINE=InnoDB DEFAULT CHARSET=gbk;

DROP TABLE IF EXISTS `mail_model_extend`;create TABLE mail_model_extend(id int(6) auto_increment not null primary key,rid varchar(50) not null,content varchar(2000),INDEX (RID),FOREIGN KEY (RID) REFERENCES mail_model(ID) ON DELETE CASCADE ON UPDATE CASCADE)ENGINE=InnoDB DEFAULT CHARSET=gbk;