mysql DDL 列操作

 

增加字段

alter table user add email varchar(100);

alter table user add hobby varchar(100) default '' not null;

 

修改字段类型、长度、默认值

alter table user modify email int;

alter table user modify email int(4);

alter table user modify email varchar(50);

alter table user modify email int(4) default 0;

默认值

alter table user modify email varchar(100) default null;

alter table user modify email varchar(100) default '';

添加注释

alter table user modify email varchar(50) default '' not null  comment '电子邮件';

指定在某个字段的后面

alter table user add email varchar(100) after id;

调整字段位置

alter table user modify email varchar(100) after sex;

 

删除字段

alter table user drop column email;

 

重命名列

alter table user change email email2 varchar(100);

alter table user change email2 email varchar(100) not null default '' comment 'email';

 

重命名表

alter table user2 rename user;

 

加唯一限制

alter table user add unique uq_email(email);

 

删除唯一限制

alter table user drop index uq_email;

 

查看表的创建语句

show create table user;

 

增加外键,级联更新

 

alter table role_user 

add constraint fk_user foreign Key (user_id)

references user (id) on update cascade on delete cascade;