mysql 添加 删除索引(index)

* 建表语句

CREATE TABLE `config` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL COMMENT '配置项',
  `value` varchar(255) NOT NULL COMMENT '配置值',
  PRIMARY KEY (`id`),
  UNIQUE KEY `uniq_config_name` (`name`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

* 添加索引

alter table `config` add index idx_config_name(`name`);

* 删除索引

alter table `config` drop index idx_config_name;

* explain 查看是否使用到了索引

insert into config(name, value, info) values('SMS_ENABLED', '0', '0表示禁用发短信功能, 1表示启用发短信功能');

explain select * from config where name='SMS_ENABLED';

+------+-------------+--------+-------+----------------------------------+------------------+---------+-------+------+-------+
| id   | select_type | table  | type  | possible_keys                    | key              | key_len | ref   | rows | Extra |
+------+-------------+--------+-------+----------------------------------+------------------+---------+-------+------+-------+
|    1 | SIMPLE      | config | const | uniq_config_name,idx_config_name | uniq_config_name | 194     | const |    1 |       |
+------+-------------+--------+-------+----------------------------------+------------------+---------+-------+------+-------+
 

* 查看mysql版本号

> select version();
+-----------------+
| version()       |
+-----------------+
| 10.1.34-MariaDB |
+-----------------+