[.characters.]
Within a bracket expression (written using [ and ]), matches the sequence of characters of that collating element.
mysql> SELECT '~' REGEXP '[[.~.]]'; -> 1
为啥不是单[?结果也是 1 呀
mysql> SELECT '~' REGEXP '[.~.]';
[=character_class=]
Within a bracket expression (written using [ and ]), [=character_class=] represents an equivalence class.
里面没举例,可否写个例子?
[:character_class:]
Within a bracket expression (written using [ and ]), [:character_class:] represents a character class that matches all characters belonging to that class.
mysql> SELECT 'justalnums' REGEXP '[[:alnum:]]+'; -> 1
为啥不是单[?结果也是 1 呀
mysql> SELECT 'justalnums' REGEXP '[:alnum:]+';
[[:<:]], [[:>:]]
These markers stand for word boundaries. They match the beginning and end of words, respectively.
怎么需要 2 个来分别表示?
这是一个专为移动设备优化的页面(即为了让你能够在 Google 搜索结果里秒开这个页面),如果你希望参与 V2EX 社区的讨论,你可以继续到 V2EX 上打开本讨论主题的完整版本。
V2EX 是创意工作者们的社区,是一个分享自己正在做的有趣事物、交流想法,可以遇见新朋友甚至新机会的地方。
V2EX is a community of developers, designers and creative people.