August 2022
Beginner to intermediate
463 pages
9h 22m
Chinese
Content preview from Tableau Prep即学即用
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｜
417
保持数据更新
47.4
刷新数据源时的注意事项
在
Prep Builder
中设置刷新流程时，需要评估以下几个方面，以确定
Prep
流程的结
果是否符合预期。
47.4.1
更改数据值
在设置向现有数据集添加新数据行的增量刷新时，也必须考虑现有记录。如果这些
记录有可能被更新，则应该定期进行完全刷新，以确保对现有记录的任何更新也反
映在数据中。否则，由于新的数据行被添加，数据集的大多数用户会错误地认为所
有数据都是最新的。
47.4.2
改变数据源的结构
添加的新列将被转换到新的数据记录中（例如，新的数据月份）和流程中非预期的
新列之间是有区别的。可以将通配符转换选项应用于新的日期列，以防止那些错误
或意外的后果（见图
47-6
）。
图
47
-
6
：使用通配符转换来增强数据结构的后续适应性
对于意料之外的新列，很难预测输出会受到怎样的影响。存在以下这些可能：
•
如果没有转换，数据仍有可能输出，但可能不包括新列。
•
在汇总步骤将中删除新的数据列，因为它在该步骤中没有使用，除非通过
self-
join
（自连接）将该数据集添加回来，否则它不会出现在输出中。
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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.
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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.