POSIX搜索可变长度字符串

Question

我有以下三个字符串，我想捕获四个示例中每个示例的branch_number结果。我正在使用PostgreSQL 8.4

ex.1) "decision => approved ,  branch_number => 1126 , alpha"
ex.2) "decision => counter ,  branch_number => 249 , beta"
ex.3) "decision => declined ,  branch_number =>NULL, gamma"
ex.4) "decision => declined ,  branch_number => 91"

我当前的查询如下，相应的结果和预期结果：

trim(substring(replace(e.meta,'_','') from '%branchnumber =>#"_____#"%' for '#'))

results 1) "1126" (desired "1126")
results 2) "249" (desired "249")
results 3) "NULL," (desired "NULL")
results 4) <null> (desired "91")

我无法确定＃限定符之间的内容，因为结果集可能是2位数的空格，3位数的空格，4位数的空格，或者只是4个文本字符。

Answer 1

使用以下正则表达式解决

trim(substring(e.meta from '%branchnumber =>([A-Z]{4}| [0-9]{1,5}))