Chapter 10: Data Blending: Join Types Explained

In the previous lessons we discussed the foundations of data blending: what data blending is and how it works behind the scenes mainly using the Left Outer Join Type.

We learned how useful data blending can be for us to bring up to five data sources (e.g. Google Analytics, Google Sheets, Facebook Ads data source, etc.) together into a single, blended data source so we can visualize it on a chart.

In this chapter we will learn about the other join types aside from Left Outer Join.

10.1. Intro & Limitations of Old Data Blending

Welcome to the advanced course on data modeling and data blending in Looker Studio! In our last session, we explored the foundations of data blending and discussed the left outer join. Today, we'll dive deeper into the rest of the join types available in Looker Studio, starting with some examples of the left join.

Data Blending: A Refresher

Remember, in Looker Studio, we can only use one data source per chart. However, we can blend data sources based on specific criteria and join keys, essentially creating a single blended data source. This allows us to connect multiple data sources to a single chart.

Initially, data blending had some limitations:

A maximum of five data sources could be blended.
Only left outer join was supported.
The same join key needed to be present in all data sources.

While the limitation of blending up to five data sources still exists, we now have access to multiple join types and keys across different joins.

Expanded Join Types

In addition to the left outer join, Looker Studio now offers right, inner, full outer, and cross join types. This provides greater flexibility in how you can mix and match different join types between tables. For example, you might want a left join between the first and second tables, a full outer join between the second and third tables, and a cross join for the final table.

Understanding Join Types with Venn Diagrams

Venn diagrams are often used to illustrate different join types. These overlapping circles show how data from different tables is combined based on the join type being used.

Let's take a closer look at the various join types in Looker Studio and how they can be applied in real-life scenarios.