数据库的简单操作02

create table t11(
id tinyint(4) not null primary key auto_increment,
name varchar(20) not null
)engine=innodb default charset=utf8;

insert into t11 values
    (1,'xx'),
    (2,'cc');

varchar(20) not null; 

alter table t11 change name username varchar(10);

 varchar(20) not null default 'aa';
alter table t11 add sex enum('男','女'); 

alter table t11 drop sex;

rename table t11 to t121;

alter table t121 rename as t11;

alter table t11 change id id int(8) unsigned;
alter table t11 drop primary key;

alter table t11 add unique name_unique(username);#uni

alter table t11 drop index name_unique;

alter table t11 add index index_name(username);#mul
alter table t11 drop index index_name;

show indexes from t11;