Tableau 简明教程
Tableau - Extracting Data
Tableau 中的数据提取从数据源中创建数据子集。这通过应用筛选器来提高性能很有用。它还有助于将 Tableau 的一些功能应用于数据，而这些功能可能在数据源中不可用，例如查找数据中的不同值。但是，数据提取功能最常用于创建要存储在本地驱动器中的提取，以便 Tableau 可脱机访问。
Data extraction in Tableau creates a subset of data from the data source. This is useful in increasing the performance by applying filters. It also helps in applying some features of Tableau to data which may not be available in the data source like finding the distinct values in the data. However, the data extract feature is most frequently used for creating an extract to be stored in the local drive for offline access by Tableau.
Creating an Extract
通过菜单“数据 → 提取数据”完成数据提取。它会创建许多选项，例如对要提取的行数应用限制以及是否要聚合维度数据。以下屏幕显示了“提取数据”选项。
Extraction of data is done by following the menu - Data → Extract Data. It creates many options such as applying limits to how many rows to be extracted and whether to aggregate data for dimensions. The following screen shows the Extract Data option.
Applying Extract Filters
要从数据源中提取数据子集，您可以创建筛选器，这些筛选器将仅返回相关行。让我们考虑 Sample Superstore 数据集并创建提取。在筛选器选项中，选择“从列表中选择”，然后选中要从源中提取数据所需复选框值。
To extract a subset of data from the data source, you can create filters which will return only the relevant rows. Let’s consider the Sample Superstore data set and create an extract. In the filter option, choose Select from list and tick mark the checkbox value for which you need to pull the data from the source.
Adding New Data to Extract
要为已创建的提取添加更多数据，可以选择选项“数据 → 提取 → 从文件中附加数据”。在此情况下，浏览包含数据的文件，然后单击“确定”以完成。当然，文件中的列数量和数据类型应与现有数据同步。
To add more data for an already created extract, you can choose the option Data → Extract → Append Data from File. In this case, browse the file containing the data and click OK to finish. Of course, the number and datatype of columns in the file should be in sync with the existing data.
