如果我截断一个表，是否还应该添加索引？
如果截断表，则不需要添加索引，因为截断表后会重新创建表，并且会自动添加索引。
让我们首先创建一个表-
mysql> create table DemoTable -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> FirstName varchar(20), -> LastName varchar(20) -> );
以下是创建索引的查询-
mysql> create index Index_firstName_LastName on DemoTable(FirstName,LastName); Records: 0 Duplicates: 0 Warnings: 0
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable(FirstName,LastName) values('John','Smith');截断表格之前，您需要检查表格状态-
mysql> show create table DemoTable;
输出结果
这将产生以下输出-
+--------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Table | Create Table| +--------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | DemoTable | CREATE TABLE `DemoTable` (`Id` int(11) NOT NULL AUTO_INCREMENT,`FirstName` varchar(20) COLLATE utf8_unicode_ci DEFAULT NULL,`LastName` varchar(20) COLLATE utf8_unicode_ci DEFAULT NULL,PRIMARY KEY (`Id`),KEY `Index_firstName_LastName` (`FirstName`,`LastName`)) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci | +--------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)
现在截断表-
mysql> truncate table DemoTable;
现在再次检查表状态。您不需要添加索引-
mysql> show create table DemoTable;
输出结果
这将产生以下输出-
+--------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Table | Create Table | +--------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | DemoTable | CREATE TABLE `DemoTable` (`Id` int(11) NOT NULL AUTO_INCREMENT,`FirstName` varchar(20) COLLATE utf8_unicode_ci DEFAULT NULL,`LastName` varchar(20) COLLATE utf8_unicode_ci DEFAULT NULL, PRIMARY KEY (`Id`),KEY `Index_firstName_LastName` (`FirstName`,`LastName`)) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci | +--------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)