标签：first weight letter res rop ima cte unique ica
（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: 0 mysql> 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: 0 mysql> 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 | +-------+---------------------------------------------------------------------------------------------------------------------------------------------------+
标签：first weight letter res rop ima cte unique ica
原文地址：https://www.cnblogs.com/hb15988111121/p/12808743.html
