Summary
We began this chapter with an introduction to relationships, followed by a discussion on complex joins, and discovered that, when possible, Tableau uses join culling to generate efficient queries to the data source. A secondary join, however, limits Tableau's ability to employ join culling. An extract results in a materialized, flattened view that eliminates the need for joins to be included in any queries. Unions come in handy if identically formatted data, stored in multiple sheets or data sources, needs to be appended.
Then, we reviewed data blending to clearly understand how it differs from joining. We discovered that the primary limitation in data blending is that no dimensions are allowed from a secondary source; however, we also discovered that there are exceptions to this rule. We also discussed scaffolding, which can make data blending surprisingly fruitful.
Finally, we discussed data structures and learned how pivoting can make difficult or impossible...