Home Database Mysql Tutorial 如何去除Oracle库表结构中的类空格字符

如何去除Oracle库表结构中的类空格字符

Jun 07, 2016 pm 05:04 PM

在涉及数据库操作的工作中,我们常会遇到对2个字符串进行等值比较而非模糊查询:例如比较2个姓名是否相等?但操作人员在将字符串

在涉及数据库操作的工作中,我们常会遇到对2个字符串进行等值比较而非模糊查询:例如比较2个姓名是否相等?但操作人员在将字符串录入系统的时候,可能会录入空格,或者是TAB健(我把这样的看起来像空格,可能实际上并不是空格的字符称为类空格字符),这样在比较的时候肯定是不等的。怎么办?

1.首先是去除空格在进行比较(比如,把姓名中的所有空格去除):

Update table_name set xm=replace(xm , ' ') ;

如果要查找哪些记录含有' ',可用相关的语句查找。

然后可进行比较。

2.但是我们可能会发现,有些姓名中间或末尾还有类似空格的字符没被去掉,但它们显然已经不是一般的空格了,那么怀疑是Tab健作怪。于是参照网上说的去掉TAB键的办法来处理,用chr(9)来替代空格键(TAB键的ASCII值为9)。先取一条带有类空格字符的记录来做实验:

SELECT replace(xm, chr(9) ) from table_name where bh=’xxx’;

用这个办法会去掉一些真正的Tab键空格,然后采取批量更新的办法。

3.但我遇到的情况没有这么幸运,没能去掉类空格键。怎么办呢?我决定尝试先取得这个类空格键的ASCII码值,,然后再用chr(ASCII码值)的方法来处理。

①.取得含类空格键整个字符串的长度 length(),从而确定出类空格键在字符串中的起始位置、类空格键的长度。

②.求出类空格键的ASCII码值:ascii(substr(xm,n,m)); n为类空格键的起始位置;m为长度。

③.SELECT replace(xm, chr(第②步求得的ASCII码值) ) from table_name where bh=’xxx’;

问题得以解决。但我发现,上述第②步求得的ASCII码值为41377,这应该是一个汉字的ASCII码值,看起来又像空格,于是我怀疑,会不会是中文状态下的空格键、TAB键?尝试之后发现不是。我又怀疑,是不是全角、半角的区别?因为我们一般输入字符,是在半角下输入的。我按照第一步“1.首先是去除空格在进行比较……”尝试,输入全角下的空格,进行查找,结果惊喜出现,原来所有未剔除掉的类空格,是全角状态下输入的空格,并接证实了全角下输入的空格,其ASCII码值为41377。

最后发现,杀鸡用了牛刀,因为问题很简单。但采用第3.提到的先取得ASCII码值再来进行剔除的方法,具有通用性!

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