

Identify the join condition (join key). At least one dimension must be used between the data sources that have identical values between data sources. The date is a very common join condition when one needs to sum up PPC metrics like Impressions, Clicks and Spend. The campaign is very common when trying to report total engagement with a Campaign that is identical across multiple data sources.
Under Blend Data, select a Table 1 and Table 2 and click Configure join.
In Join configuration, select a Join operator to use.
Under Join conditions, click Add field for the left and right tables to add a field from each table. Note: A cross join does not accept any conditions.
Understanding joins: Data Studio allows the use of five different types of joins for blending.
Left outer join: The data source chosen on the far left of your blend will combine only with the data source(s) to the right that shares the same key values. If the far left data source does not have data for a particular day, the blended data will also not contain that data. We see this happen quite frequently when clients try to blend data and then ask us why there are dates missing data.
Because of this limitation, you must choose the far left data source wisely! Make sure the data source has data every day in the date range you want to report. And as a hack, if the particular metric(s) you want to report do not have data every day, add additional metrics that you may not use just to populate 0's for the rest of the data you do want to use. For example, there may be no Transactions on certain days in Google Analytics for your data source. Add Sessions to the list of metrics so that Transactions must populate with 0's in the output to Data Studio.
The left outer join operation means only data in the left circle will report in Data Studio.
Right outer join: The data source chosen on the right of your blend will combine only with the data source to the left that shares the same key values. If the right data source does not have data for a particular value, the blended data will not contain that data. Only data in the right circle will report in Data Studio.
Inner join: Only rows that match in both the left and right data sources will report in Data Studio. Rows in the left or right data source only without a corresponding row in the other data source will not be reported.
Full outer join: All matching rows from both the left data source and the right data source will be reported inclusively in Data Studio.
Cross join: A cross join is a cross-product of the left and right data sources without any conditions, and can produce a very large result set. The number of rows returned will be the number of rows in the left data source multiplied by the number of rows in the right data source. Using a cross join can cause a “too much data requested” error.
