索引的增删改成查

Posted 2020-10-12 程绩

1 创建表时就指定索引

create table t1(

　　id int,

　　name char(5),

　　unique key nui_name(name),

　　primary key (id)

);

create table t2(

　　id int,

　　name char(5),

　　index idx_name(name)

);

2 在创建完表后为其添加索引

create table t3(

　　id int,

　　name char(5)

);

create inde idx_name on t3(name);

alter table t3 add index idx_id(id);

alter table t3 add primary key(id);

查看
mysql> show create table t3;
+-------+-------------------------------------
| Table | Create Table
+-------+-------------------------------------
| t3 | CREATE TABLE `t3` (
`id` int(11) DEFAULT NULL,
`name` char(5) DEFAULT NULL,
KEY `idx_name` (`name`),
KEY `idx_id` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+-------+-------------------------------------
1 row in set (0.00 sec)

删除
drop index idx_id on t3;

alter table t3 drop primary key;