mysql 强大的trim() 函数

mysql中的去除左空格函数：
ltrim(str)
returns the string str with leading space characters removed.

以下是代码片段：

mysql> select ltrim(' barbar');
-> 'barbar'

this function is multi-byte safe.

mysql中的去除右空格函数：
rtrim(str)
returns the string str with trailing space characters removed.

以下是代码片段：

mysql> select rtrim('barbar ');
-> 'barbar'

this function is multi-byte safe.

trim函数可以过滤指定的字符串：
完整格式：trim([{both | leading | trailing} [remstr] from] str)
简化格式：trim([remstr from] str)

returns the string str with all remstr prefixes or suffixes removed. if none of the specifiers both, leading, or trailing is given, both is assumed. remstr is optional and, if not specified, spaces are removed.

以下是代码片段：

mysql> select trim(' bar '); //默认删除前后空格
-> 'bar'
mysql> select trim(leading '，' from '，，barxxx'); //删除指定首字符 如'，‘
-> 'barxxx'
mysql> select trim(both '，' from '，，bar，，，'); //删除指定首尾字符
-> 'bar'
mysql> select trim(trailing '，' from 'barxxyz，，');
-> 'barxxyz'

mysql> update table set `field`=trim(trailing ',' from `field`) where where `field` like '%,';

this function is multi-byte safe.

替换数据库中字段的最后一个分页符

update [!db.pre!]ecms_news_data_1 set `newstext`=trim(trailing '[!--empirenews.page--]' from `newstext`) where id=585;
select trim(trailing '[!--empirenews.page--]' from `newstext`) as newstex from [!db.pre!]ecms_news_data_1 where id=585;