|
|
|
MySQL中两种快速创建空表的方式的区别http://www.sina.com.cn 2008年06月10日 07:47 赛迪网
作者:Chad 【赛迪网-IT技术报道】在MySQL中有两种方法 1、create table t_name select ... 2、create table t_name like ... 第一种会取消掉原来表的有些定义,且引擎是系统默认引擎。 手册上是这么讲的:Some conversion of data types might occur. For example, the AUTO_INCREMENT attribute is not preserved, and VARCHAR columns can become CHAR columns. 第二种就完全复制原表。
先建立测试表:
mysql> create database dbtest; Query OK, 1 row affected (0.03 sec)
mysql> use dbtest; Database changed mysql> create table t_old -> ( -> id serial, -> content varchar(8000) not null, -> `desc` varchar(100) not null) -> engine innodb; Query OK, 0 rows affected (0.04 sec)
mysql> show create table t_old; +-------+-------------------------------------------------+ | Table | Create Table | +-------+------------------------------------------------+ | t_old | CREATE TABLE `t_old` ( `id` bigint(20) unsigned NOT NULL auto_increment, `content` varchar(8000) NOT NULL, `desc` varchar(100) NOT NULL, UNIQUE KEY `id` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 | +-------+----------------------------------------------------+ 1 row in set (0.00 sec)
第一种方式:
mysql> create table t_select select * from t_old where 1 = 0; Query OK, 0 rows affected (0.04 sec) Records: 0 Duplicates: 0 Warnings: 0
mysql> show create table t_select; +----------+--------------------------------------------+ | Table | Create Table +----------+---------------------------------------------+ | t_select | CREATE TABLE `t_select` ( `id` bigint(20) unsigned NOT NULL default '0', `content` varchar(8000) NOT NULL, `desc` varchar(100) NOT NULL ) ENGINE=MyISAM DEFAULT CHARSET=latin1 | +----------+-------------------------------------------+ 1 row in set (0.00 sec)
第二种方式:
mysql> create table t_like like t_old; Query OK, 0 rows affected (0.02 sec)
mysql> show create table t_like; +--------+-------------------------------------------------+ | Table | Create Table | +--------+-------------------------------------------------+ | t_like | CREATE TABLE `t_like` ( `id` bigint(20) unsigned NOT NULL auto_increment, `content` varchar(8000) NOT NULL, `desc` varchar(100) NOT NULL, UNIQUE KEY `id` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 | +--------+-------------------------------------------------+ 1 row in set (0.00 sec)
mysql> (责任编辑:卢兆林)
【发表评论 】
|