August 2022
Beginner to intermediate
463 pages
9h 22m
Chinese
Content preview from Tableau Prep即学即用
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｜
267
去除重复数据
图
30
-
1
：使用 Case ID 来识别行数
30.2
重复的原因
现在你已经知道在示例数据集中有重复的数据，让我们看看一些潜在的原因。
30.2.1
系统加载
由于运营系统会跟踪订单状态、客户投诉和库存，因此会在不同的时间点获取运营
状态。对于每条记录，如果之前的状态还被存储着，没有被新的状态覆盖，就会产
生重复。
在如图
30-2
所示的例子中，
Status
（状态）字段会随着公司处理订单的时间而更新。
只有
Case ID
的独立计数才会返回正确的订单数，因为独立计数只对一个值计算一
次，而忽略它的后续实例。
如果你需要一个单独的计数，你可以使用
Aggregate
（汇总）步骤创建一个计数。
Aggregate
（汇总）步骤在第
15
章有介绍。
268
｜
第
30
章
图
30
-
2
：每种 Status（状况）增设一行后产生的重复数据
30.2.2
每项度量的行
如果每一行都包含一个单独的度量，也会造成重复。在如图
30-3
所示的数据集中，
你必须在
Store
（商店）和
Type
（类型）字段上使用不同的计数，以统计销售每种
类型产品的商店数量。然而，区分计数需要大量的计算资源，因此在分析数据时，
这并不是一种非常有效的工作方式。
图
30
-
3
：数据结构导致的重复数据
｜
269
去除重复数据
30.2.3
连接
在对不具备精确的同类数据连接条件的数据进行连接操作时，所得到的数据集可能 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
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.