如何使用RegEx返回已解析的值？ [英] How do you use RegEx to return a parsed value?

问题描述

我有一个数据列，具有多个级别的标题值，我只想要前三个级别，但是我不知道如何获得解析的值？

I have a data column that has a heading value with multiple levels, where I only want the first three levels, but I cannot figure out how to get the parsed value?

我正在阅读此，并显示如何使用创建一个函数来返回一个布尔值，但是如何创建一个返回一个被解析的值的函数？

I was reading this and it shows how to use create a function to return a boolean for the condition, but how would I create a function that would return a parsed value?

这是我认为的正则表达式

This is the Regular Expression that I think I need.

^(\d.\d.\d)

我正在寻找可以将 1.2.3.4.5。更改为 1.2.3 和类似的任何其他标题我有三个以上的水平。

I'm looking for something that would change 1.2.3.4.5. to 1.2.3 and similar for any other header I have that has more than three levels.

理想情况下，我想可以把它放入我的查询设计作为一个字段表达式，但我不知道该怎么做。

Ideally, I'd like to be able to put it into my Query Design as a Field Expression, but I'm not sure how I would do that.

推荐答案

我假设您的输入值可能在点之间有多个数字。换句话说，我想你想要这个...

I assumed your input values could have more than one digit between the dots. In other words, I think you want this ...

? RegExpGetMatch("1.2.3.4.5.", "^(\d+\.\d+\.\d+).*", 1)
1.2.3
? RegExpGetMatch("1.27.3.4.5.", "^(\d+\.\d+\.\d+).*", 1)
1.27.3

如果这是正确的行为，这里是我使用的功能。

If that is the correct behavior, here is the function I used.

Public Function RegExpGetMatch(ByVal pSource As String, _
    ByVal pPattern As String, _
    ByVal pGroup As Long) As String

    'requires reference to Microsoft VBScript Regular Expressions
    'Dim re As RegExp
    'Set re = New RegExp
    'late binding; no reference needed
    Dim re As Object
    Set re = CreateObject("VBScript.RegExp")

    re.Global = True
    re.Pattern = pPattern
    RegExpGetMatch = re.Replace(pSource, "$" & pGroup)
    Set re = Nothing
End Function

另请参阅此答案，由 kazJaw 。他的答案告诉我如何使用 RegExp.Replace 选择匹配组。

See also this answer by KazJaw. His answer taught me how to select the match group with RegExp.Replace.

在Access中运行的查询会话，你可以使用这样的功能：

In a query run within an Access session, you could use the function like this:

SELECT
    RegExpGetMatch([Data Column], "^(\d+\.\d+\.\d+).*", 1) AS parsed_value
FROM YourTable;

请注意，自定义VBA函数不可用于从Access会话之外运行的查询。

Note however a custom VBA function is not usable for queries run from outside an Access session.

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