Differences between joins and data blending Data blending simulates a traditional left join. The main difference between the two is when the join is performed with respect to aggregation. Left join When you use a left join to combine data, a query is sent to the database where the join is performed. Using a left join returns all rows from the left table and any rows from the right table that has a corresponding row match in the left table. The results of the join are then sent back to and aggregated by Tableau. For example, suppose you have the following tables. If the common columns are User ID and Patron ID , a left join takes all the data from the left table, as well as all the data from the right table because each row has a corresponding row match in the left table. Data blending When you use data blending to combine data, a query is sent to the database for each data source that is used on the sheet. The results of the queries, in...