Tableau Prep: Up & Running

Chapter 33. Creating Level of Detail Calculations

As you’ve seen, joining data sets together is a very common task in data preparation. But there is one use of joins that needs highlighting due to its slightly different use—a technique called appending. Within Tableau’s suite of products, appending is often used in Level of Detail (LOD) calculations, even if you don’t realize you are doing it.

This chapter will use LOD calculations to show the benefits of appending values to your data set for easier analysis. LOD calculations can be tricky to learn, so this chapter will walk you through what the LOD calculation is actually doing to the data set to cement your understanding.

What Is Appending?

Appending is the addition of a data field, or fields, onto an existing data set. This sounds very similar to joining, but we use the term append when adding a field that contains a constant, or set of constants, rather than the more row-to-row relationship that is found within joins.

Exploring Appending Through LOD Calculations

As Prep Builder is designed to prepare data for Tableau Desktop and Server, many of you likely will be familiar with Level of Detail calculations from using them within Desktop. If not, let’s have a quick recap.

When to Use an LOD Calculation

Tableau sets a measure’s level of aggregation by the granular dimension, or combination of dimensions, used within the view of Tableau Desktop. In the example in Figure 33-1, using data from Tableau’s sample data set Superstore, ...