MySQL ALTER命令

一、列操作1.添加列alter table one add column uname char(10);2.修改列的数据类型alter table one modify column uname char(5);3.修改列名alter table one change column uid userid int;4.删除列alter table one drop column uname;二、字段约束1.添加primary key主键alter table one add primary key (userid);2.添加foreign key外键alter table one add foreign key (uerxb) references two (usex);note:参考表字段一定要是该表的主键3.删除主键alter table one drop primary key;三、修改表名alter table two rename to other;