August 2022
Beginner to intermediate
463 pages
9h 22m
Chinese
Content preview from Tableau Prep即学即用
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406
｜
第
46
章
我们可以用这个表把客户的名字添加到如图
46-1
所示的采购表中。这个表中的客户
ID
必须是唯一的，因为我们不希望把订单归属于错误的客户。在采购表中，客户
ID
可以归为外键，因为列中的值是重复的，但可以用来连接客户表。
46.3
在
Tableau Prep
中使用键和标识符
Prep Builder
中的键与数据库中的键非常相似，它们指导用户如何将表连接在一起。
关于数据库表中哪些数据字段是键的信息可能存储在单独的数据库文档中。
Prep
Builder
对键的显示与其他数据字段没有任何不同，你可以在连接条件中像其他数据
字段一样使用它们。这就是
Join
（连接）配置窗格特别方便的地方，你可以看到哪
些值是匹配的，以及连接步骤所创建的记录的行数（见图
46-3
）。
图
46
-
3
：在 Prep 中设置 Join（连接）
当连接事实表（如
Purchases
采购表）时，你会期望保留原来的记录行数。记住，
事实表是包含测量或度量的数据库表。如果所产生的行数与原始事实表不一致，那
么可能是因为：
•
增加了记录行数。你已经重复购买了，简单的计数或数值的汇总可能会过多地
反映实际情况。
｜
407
在数据中使用标识符和键
•
记录行数减少了。你丢失了数据的记录行数，意味着销售记录或客户数量将被
低估。
Prep Builder ...
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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.