August 2022
Beginner to intermediate
463 pages
9h 22m
Chinese
Content preview from Tableau Prep即学即用
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242
第
27
章
空值处理
在数据准备工作中，
null
（空值）或数据缺失是一头变幻莫测的野兽。有经验的数
据准备者几乎本能地知道如何处理它们，或者至少知道如何面对包含它们的数据集
所带来的挑战。不过，数据准备新手并没有相同的案例或经验可以借鉴，所以本章
将介绍处理包含空值的数据集的基本注意事项。
27.1
什么是空值
数据的缺失与数字
0
（零值）、新数据行或空格都不同，零值实际上都是值。空值
出现在数据集中的原因有很多，包括：
•
它们是进行联合操作后，数据中字段不匹配的结果。
•
它们是进行左、右或完全外连接操作后，数据中字段不匹配的结果。
•
该记录没有原始数据输入，但数据集中存在其他数据点（即其他字段非空的）。
Prep Builder
在其概况窗格中显示了所有数据字段的空记录数（见图
27-1
）。
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