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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。
第一种有两个缺点
1、第一种会取消掉原来表的有些定义。
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.
不过我测试过,只会取消自增属性!
2、引擎是系统默认引擎。
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 | 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=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: 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=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 | create table |
+--------+---------------------------------------------------------+
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