The four basic SQL join types are all supported by Tableau: inner, left, right, and full outer. Prior to joining data, you must verify that the data types from the common field used in the join are the same:

Type of join	Description	Venn diagram of join
Inner join	The result set includes all records that have a matching value in both tables. For the Global Superstore Orders 2016 example, this will return all records from the Orders table for which there is a matching person in the People table.
Left join	The result set includes all records from the left table (Orders) and matching records from the People table. For records where there is no match, NULL values will appear.
Right join	The result set includes all records from the right table (People) and matching records from the Orders table. For records where there is no match, NULL values will appear.
Full outer join	The result set includes all records from both tables regardless of whether there is a match or not.

Some instructions for joins are as follows:

1. Click and drag (or double-click) the second table from the left pane onto the canvas.
2. Tableau will automatically attempt to detect a common field from both data sources in order to join both tables.
3. Click the Join icon to change the join type or to change the join operation by adding/removing additional clauses. When finished, close the Join dialog box.
4. Validate the join so that the data pane will reflect how you want the data to be ingested by Tableau in the data grid. To remove a join, click the x button icon by the join condition.

Next, we will move on to a similar type of join – the cross-database join.