regex - PostgreSQL 正则表达式单词边界？

Question

PostgreSQL 是否支持\b？

我正在尝试 \bAB\b 但它不匹配任何内容，而 (\W|^)AB(\W|$) 匹配。这 2 个表达式本质上是相同的，不是吗？

Answer 1

PostgreSQL 使用 \m , \M , \y和 \Y作为单词边界:

\m   matches only at the beginning of a word
\M   matches only at the end of a word
\y   matches only at the beginning or end of a word
\Y   matches only at a point that is not the beginning or end of a word 

参见 Regular Expression Constraint Escapes在手册中。

还有[[:<:]]和 [[:>:]] , 匹配单词的开头和结尾。来自 the manual :

There are two special cases of bracket expressions: the bracket expressions [[:<:]] and [[:>:]] are constraints, matching empty strings at the beginning and end of a word respectively. A word is defined as a sequence of word characters that is neither preceded nor followed by word characters. A word character is an alnum character (as defined by ctype) or an underscore. This is an extension, compatible with but not specified by POSIX 1003.2, and should be used with caution in software intended to be portable to other systems. The constraint escapes described below are usually preferable (they are no more standard, but are certainly easier to type).