August 2022
Beginner to intermediate
463 pages
9h 22m
Chinese
Content preview from Tableau Prep即学即用
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｜
355
支撑你的数据
计算能力
不是每个人都有一台全新的、功能强大的计算机来使用。将大量的行添加到（可
能）已经很大的数据集中，对你的计算机的工作内存真的会形成考验。
在数据源层面进行过滤，可以显著降低数据支撑对数据大小的影响。
39.4
传统的数据支撑技术
数据支撑的应用由来已久，传统的技术是使用所有可能值进行支撑。回到移动提供
商的例子，我们需要创建一个新的
Date
（日期）字段，包含数据集中从最早的合同
开始日期到最晚的合同结束日期的每个月（见图
39-5
）。
图
39
-
5
：用于支撑的数据集
356
｜
第
39
章
如你所见，最久的合同从
2019
年
1
月开始，持续
24
个月，所以我们需要的最晚日
期是
2020
年
12
月。不过仅仅有所需的日期范围是不够的。这个支撑需要加入客户
数据。要做到这一点，我们有两个选择：
•
创建一个计算，将合同的最后一个月定义为结束日期，然后使用
Start
Date>=Scaffold Date
（开始日期大于等于支撑日期）和
End Date<=Scaf fold
Date
（结束日期小于等于支撑日期）的条件加入客户数据。
•
创建一个条件，将每个数据集中的每一行连接在一起。这样就可以对其进行过滤，
以删除所有多余的行。最容易连接的计算只有数字
1
。在每个数据集中创建这个
计算，并采用
1
的条件进行连接 ...
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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.