August 2022
Beginner to intermediate
463 pages
9h 22m
Chinese
Content preview from Tableau Prep即学即用
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｜
221
在输入过程中删除数据
24.4
删除记录
通过更改列的数据类型，你可以更改数据集中的值。如果一列包含任何非数字字符，
并且将该列的数据类型更改为数字，
Tableau Prep
将用空值替换非数字值。让我们
来看一个例子。
要更改数据类型，可单击输入步骤内元数据网格中的
Data Type
（数据类型）图标。
在图
24-9
中，我们要将
String-default
（字符串
-
默认）改为
Number
（
whole
）
[
数字（整
数）
]
。
图
24
-
9
：更改 Prep 元数据网格中的数据类型
然而，元数据网格中显示的样本值已经从之前的字符串值变为
null
（空值），如图
24-10
所示。
图
24
-
10
：图
24
-
9
的变化结果
222
｜
第
24
章
如果不需要流程中那些结果为空值的记录，它们也可以被过滤掉。只需在概况窗格
中点击空值，就可以选择将其排除。这个过程也可以发生在概况窗格中。让我们看
看另一个例子，这次是
Preppin
’
Data 2019
：第
2
周挑战赛中的
Value
列（
https://
oreil.ly/EGUmO
），数据集被拆分为两个表，创建了第二组标题。图
24-11
展示了
数据类型转换前的数据字段。
图
24
-
11
：Value（值）数据字段中值的样本
将
Value
列的数据类型从字符串改为数字，将字符串值改为
null
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and much more.
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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.