Tableau Prep: Up & Running

Chapter 48. Using History Tables

Live data connections are a fantastic way to keep your analysis relevant and prevent repeated work each time a data set is updated, which may be frequently. Building data visualizations that connect to live data sets gives end users confidence that they are getting the latest view on the topic.

The challenge with frequently updating data is deciding what happens with records that are either updated or removed when no longer relevant. Building a history table allows you to record data points at a set interval without worrying that they will be overwritten and lost forever.

Why Are History Tables Required?

When analyzing data, users will ask many questions to get a comprehensive view of key trends, outliers, and unexpected results in the data set. However, once they have found these data points, users will want to know:

• Why are these trends or points showing what they do?

• Has it always been this way?

The first question relates to gathering context, and it can be tough to answer. Often, working with subject-matter experts can be helpful. The second question often boils down to having historical data to draw upon. Despite decreasing storage costs for data, however, the rapid growth of data sets can make it challenging to retain sufficient historical data points to answer the question.

Retaining too much information will swamp both the analyst and the tool. Too little history, though, and it will be impossible to judge whether a trend is present. ...