在MYSQL中快速创建空表
今天有人问我用什么方法可以创建空表？ 在MYSQL中有两种方法。1、create table select ...
2、create table like ...
第一种很多人都知道，第二种却很少人用。
第一种有个缺点:
取消掉原来表的有些定义。
手册上是这么讲的：
Someconversion of data types might occur. For example, the AUTO_INCREMENTattribute is not preserved, and VARCHAR columns can become CHARcolumns.
不过我测试过，只会取消自增属性！(可能是版本不同吧。其他版本没有测试过！)
第二种就不会。
我们来看看例子：
mysql> create table t_old (id serial, content varchar(8000) not null,`desc` varchar(100) not null) engine innodb;
Query OK, 0 rows affected (0.01 sec)
mysql> show create table t_old;
+-------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|Table | CreateTable |
+-------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| 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=utf8 |
+-------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql> create table t_select select * from t_old where 1 = 0;
Query OK, 0 rows affected (0.01 sec)
Records: 0Duplicates: 0Warnings: 0
PS:如果想要保持一样的引擎，就加上。
这样写：create table t_select engine innodb select * from t_old where 1 = 0;
mysql> show create table t_select;
+----------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|Table | CreateTable |
+----------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| 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=utf8 |
+----------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql> create table t_like like t_old;
Query OK, 0 rows affected (0.02 sec)
mysql> show create table t_like;
+--------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|Table| CreateTable |
+--------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| 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=utf8 |
+--------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
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