August 2022
Beginner to intermediate
463 pages
9h 22m
Chinese
Content preview from Tableau Prep即学即用
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215
第
24
章
在输入过程中删除数据
我们可以通过更改初始数据连接来简化很多数据准备工作，初始数据连接是在
Prep
Builder
的输入步骤中创建和显示的。然而，你知道，很多时候甚至在将数据输入
Prep Builder
之前，就需要更改或删除数据集中的某些元素。本章将介绍在早期阶段
删除数据的一些注意事项，以及如何进行删除操作。
24.1
在加载数据集之前对其进行更改
数据集正在不断迅速增长，所以必须仔细考虑实际被加载到工具中的数据内容。任
何输入数据都会加载到计算机的内存中，所以所有减少必须处理的数据量的努力都
是有用的。
Prep Builder
将在初始加载时对数据集进行采样，仅在运行输出时才处理
完整的数据集。
对于
Prep Builder
来说，初始连接是
Input
（输入）步骤，但
Prep Builder
不会立即
加载所有数据。
Prep
将在输入步骤中首先加载元数据──关于数据的数据。这对最
终用户有两个方面的帮助：
•
提供数据的快速概览。
•
防止加载时间过久，因为
Prep Builder
不需要处理所有的数据。
取消选择你和最终用户不需要的那些字段，将省去这些数据被
Prep Builder
处理的
过程（见图
24-1
）。
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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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