How to Combine Tables in Tableau?

In this article, we’ll explore how to combine data from multiple tables in Tableau. For those who prefer using Power BI, you can check out the guide here: https://davoy.tech/combining-tables-in-power-bi/.

Initially, Tableau did not support relationships, but now it offers various methods to combine tables, which can sometimes be confusing. Before diving into the methods, it’s essential to understand what a Tableau Data Source is. One Tableau Data Source is a single chunk of data that may consist of multiple tables.

In simple terms, Data Source > Table > Field.

Method 1: Union

Suppose we have monthly sales data files and want to combine them into a single table. If the columns are identical, we can use the union method to add the data as new rows. After using union, it will combine into one table within the same data source.

Method 2: Join Table

Suppose we have a sales data file with only product codes and another file with product names corresponding to the codes. We want to combine them into a single table with different columns, adding the product name as a new column on the right. We can use the join method to combine the data, choosing which field to join on and the type of join:

Inner Join: Only data that matches in both tables.
Left Join: All data from the left table.
Right Join: All data from the right table.
Full Outer Join: All data from both tables.After using join, it will combine into one table within the same data source.

Method 3: Relationship

This method creates a bridge between multiple tables, maintaining the original data in each table. When creating visuals, you can pull data from various tables simultaneously. This method suits data with different levels of detail, such as sales data and salesperson names. If you have only ten salespersons and don’t want to repeat their names in every sales record, use relationships instead of joins. After establishing a relationship, each table remains separate, and multiple tables exist within the same data source. Relationships apply to all sheets created.

Method 4: Blend Data

The oldest method in Tableau is blending data or creating links on each sheet. The advantage is that you can choose to create links on specific sheets only, but you have to create them anew every time. Nowadays, this method is less popular compared to using relationships.

You can see the summary in the table below.