August 2022
Beginner to intermediate
463 pages
9h 22m
Chinese
Content preview from Tableau Prep即学即用
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276
第
31
章
使用正则表达式
数据可能是很复杂的，它们并非仅仅把值加在一起或做计数这样的事情。例如，字
符串数据字段可能有很多复杂应用，但在使用它们形成你的数据集和分析时往往是
必不可少的。正则表达式（或称
regexes
）是一组控制命令，它使得解析起来很困难
的字符串变得更加容易解析。在本章中，我们将介绍到底什么是正则表达式，如何
在
Prep Builder
中使用它们，以及如何使用一些常用的正则表达式函数。
31.1
什么是正则表达式
正则表达式是在一串字符中搜索字符模式（例如，值
population
）的计算方法（例如，
“
The population of the United Kingdom is 66,650,000 people
”）。与我们见
过的其他字符串函数如
LEFT()
、
MID()
和
RIGHT()
相比，
Regexes
可以识别的模式
更加灵活。
学习正则表达式的一个好处是，它们在大多数的数据工具中共享一组通用的控制命
令，因此在数据准备工具之间具有高度的可移植性。另一个好处是，它们可以帮助
你无须使用本书迄今为止所介绍的简单字符串函数，却能构建非常复杂的字符串算
式。
31.2
如何在
Tableau Prep
中使用正则表达式
在
Prep
中使用正则表达式的方法主要有三种（见图
31-1
）。
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.