Looker Studio Blended Data Joins – Left Outer Join

One of the key features in data blending within Looker Studio is the ability to perform various types of joins which combine data in different ways. Among five types of joins, let’s start reviewing blended data joins in Looker Studio with Left Outer Join. 

Left Outer Join

A left outer join is a type of join that returns all records from the left table, and the matched records from the right table. If there is no match, the result is NULL on the side of the right table.

Let’s take a look, how it works in practice. 

Here we have 2 tables with Google Ads (left table) and Facebook Ads (right table). We can match the tables based on the Date. There is a match – 6th, 5th and 4th of August. The only differences are August, 9th in the left table, and August, 7th in the right table. 

As we are using Left Outer join, in the table with blended data we will have all the rows from the left table, meaning that the non-matching row from the right table (7 Aug 2022) will be eliminated. 

How to create blended data?

Let’s start from Google Ads. As dimensions we select Date, as metrics I would select only the Cost and as date range I select “auto”, or we create custom and we can add filters. Then we add another table. In our example it will be Facebook Ads. If it’s necessary, we may add one more table, and the maximum that we can add is 5 tables. Here we select dimensions and metrics that we’ll need in the report. 

In Configure Join we can click here and see 5 types of joins. Here we can select the type of join and fields and based on ones we will join. 

In Join Configuration we can choose only the dimension we have already added. In our case the dimension is the Date. It is a really common case for marketing and sales data when we take a date and try to find the same information from another table for the same date.

Our aim is just to see the common data from campaigns. Then we add the name to our blending data source.

Summary 

Hope this quick recap of what left outer join in Looker Studio is was useful for you! If you have any questions about blended data and, particularly, left outer join, I’ll be glad to help you understand!