在我没有整理数据库之前，导出数据库的表有270多M，导入这个数据库后，表空间竟然达到了20G。这是怎么回事，数据库曾经清库好几次
在我没有整理数据库之前，导出数据库的表有270多M，导入这个数据库后，表空间竟然达到了20G。
这是怎么回事，数据库曾经清库好几次，最近刚刚清库，怎么会有这么大的表空间。
我一开始认为是表里面的垃圾数据太多，清库不完整，所以导致表空间这么大，然后我对数据库进行清理，最后导出数据时已经从270M变成10M了，差距相当大。
但是当我再次导入另一个系统时，表空间依然是20G，之后我尝试导入空表，，还是20G，这时候我就想到可能是表本身的空间太大了。
看下图：
这仅仅是一个表，就有这么大的空间，肯定是由于原来这个表曾经有过几十万的数据增长到了700多M，删除数据后，表空间不变，所以就导致了上面的原因。
当我把上面的表转存到临时表的时候，显示如下：
仅仅64KB。之后我就按照下面的操作：
1.将原表全部转存到临时表
2.删除原表
3.将临时表存入原表
4.删除临时表
我重新整理完之后，我又导出了，这次从10M变成了7M多。
我在另一电脑上再次导入之后，表空间的大小连100M都没有超过，通过简单的操作，给电脑节省了20G的空间...
再操作上面4步的时候，可能有人会觉得那么多表很麻烦，我说一种我常用的方法，大家看下图：
通过excel可以批量写出样式一样的SQL语句....如果谁有更方便的方法，欢迎交流~~~~~~~~~~~~~
注意事项：上面的操作会丢失表的注释和相应的触发器等等...
这里提供一个从网上搜到的查询表空间的语句
更多Oracle相关信息见Oracle 专题页面 ?tid=12
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