August 2022
Beginner to intermediate
463 pages
9h 22m
Chinese
Content preview from Tableau Prep即学即用
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｜
139
将数据集连接到一起
16.3 Prep Builder
中的连接类型
为了探究在
Prep Builder
中使用每种连接类型所产生的影响，我们将使用两个简单
的数据集。左表（见图
16-8
）和右表（见图
16-9
）。每个示例都将演示如果我们设
置连接条件，使左表的类别与右表的类别相同，将会产生什么样的输出。
在现实世界中，
Prep Builder
的输出将包含两个表的
Category
列，但这些列
通常会被用户删除，所以我在这里只记录了一个。
图
16
-
8
：左表数据集
图
16
-
9
：右表数据集
Prep Builder
为我们提供了以下类型的连接选项：
inner
（内连接）
内连接将只返回满足连接条件的记录（见图
16-10
）。
140
｜
第
16
章
图
16
-
10
：inner（内连接）
对于示例数据集，内连接返回的
Category
（类别）值只有
A
和
B
，对应
Measure
（度
量）
1
和度量
2
的值。图
16-11
展示了结果。
图
16
-
11
：inner（内连接）的结果
left
（左连接）
左连接将返回左表的所有记录，加上右表中满足连接条件的记录。不满足连接
条件的所有右表记录将不会被带到下一步（见图
16-12
）。左表中的记录如果在
右表中没有匹配，则在生成的表中会有一个
null
（空值）。
图
16
-
12
：left（左）连接
｜
141
将数据集连接到一起 ...
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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.