（1）直接创建索引

CREATE INDEX index_name ON table(column(length))

CREATE UNIQUE INDEX zipindex on ec_address(FIRST_LETTER(3))

mysql> create index index_name on t1(id);Query OK, 0 rows affected (2.80 sec)Records: 0 Duplicates: 0 Warnings: 0mysql> show create table t1;+-------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+| Table | Create Table |+-------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+| t1 | CREATE TABLE `t1` ( `id` int DEFAULT NULL, `name` varchar(50) DEFAULT NULL, KEY `index_name` (`id`)) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci |+-------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+1 row in set (0.00 sec)

（2）修改表结构的方式添加索引

普通索引

ALTER TABLE table_name ADD INDEX index_name (column(length))

唯一索引

ALTER TABLE ec_address add UNIQUE INDEX suoyin  (FIRST_LETTER(3))

主键

alter table ec_address add primary key(ID)

（3）删除索引

DROP INDEX index_name ON table

mysql> drop index index_name on t1;Query OK, 0 rows affected (0.05 sec)Records: 0 Duplicates: 0 Warnings: 0mysql> show create table t1;+-------+---------------------------------------------------------------------------------------------------------------------------------------------------+| Table | Create Table |+-------+---------------------------------------------------------------------------------------------------------------------------------------------------+| t1 | CREATE TABLE `t1` ( `id` int DEFAULT NULL, `name` varchar(50) DEFAULT NULL) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci |+-------+---------------------------------------------------------------------------------------------------------------------------------------------------+