如果我截断表，是否还应该添加索引?
mysqlmysqli database更新于 2025/5/27 8:44:17
如果您截断表，则无需添加索引，因为截断表后会重新创建表，并且会自动添加索引。
首先我们创建一个表 −
mysql> create table DemoTable -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> FirstName varchar(20), -> LastName varchar(20) -> ); Query OK, 0 rows affected (0.65 sec)
以下是创建索引的查询 −
mysql> create index Index_firstName_LastName on DemoTable(FirstName,LastName); Query OK, 0 rows affected (1.04 sec) Records: 0 Duplicates: 0 Warnings: 0
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable(FirstName,LastName) values('John','Smith');
Query OK, 1 row affected (0.47 sec
使用 select 语句显示表中的所有记录 −
mysql> select *from DemoTable;
输出
这将产生以下输出 −
+----+-----------+----------+ | Id | FirstName | LastName | +----+-----------+----------+ | 1 | John | Smith | +----+-----------+----------+ 1 row in set (0.00 sec)
截断表之前，需要检查表状态 −
mysql> show create table DemoTable;
输出
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; Query OK, 0 rows affected (2.01 sec)
现在再次检查表状态。您不需要添加索引 −
mysql> show create table DemoTable;
输出
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)
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