Joins in Tableau plays the vital role in designing reports. In real-time, We usually design reports using database or data warehouse and we all know that the data present in database is in normalized form. So, we can’t generate reports using single table (mostly not, as per the business prospective).
For example if you want to design a tableau report for Country wise sales, Country information will be in Geography or territory table and Sales will be Sales table. In these situations we can use Tableau Joins to join Geography and Sales tables.
Tableau Joins
Following screenshot will show the available Joins in tableau
- Inner Join: It returns the records (or rows) present in both tables, If there is at least one match between columns. Please refer SQL Inner Join article to understand it better
- Left Join: It returns all the records (or rows) present in the Left table and matching rows from the right table. Please refer SQL Left Join article to understand it better
- Right Join: It returns all the records (or rows) present in the Right table and matching rows from the Left table. Please refer SQL Right Join article to understand it better
- Full Outer Join: It returns all the records (or rows) present in both Left table and the right table. All the Unmatched rows will be filled with NULL Values. Please refer SQL Full Join article to understand it better
How to Join Data in Tableau ?
In this article we will show you, How to Join Data in Tableau with live example. For this, we are going to use the data present in SQL Server so, Please refer Connecting Tableau to SQL Server article to understand the connection settings. Below screenshot will show you the data present in Employee table
Below screenshot will show you the data present in Department table
First, Drag and drop the first table or left table to field region. In this example, we are using our Employee table as left table
Next, Drag and drop the second table or right table to field region. When you dragged Department table, a pop up window will be opened to select the Join type and Joining key as shown below.
Tableau Inner Join
As we all know, Dept ID in Employee table and Id in Department table are the key columns we are going to use for Joining Employee and Department table. First, Select the Dept ID column from the Employee table as shown below
Next, Select the Id column from department table as shown below
We created simple table report with Occupation, Last name, Department name, First name on Rows and Sales Amount and Yearly income on columns. Let us see the Inner join report preview.
From the below screenshot you can observe that, Inner Join is producing 10 Rows which includes all the matching records from Employee and Department table.
Tableau Left Join
Let us change the Join type from Inner Join to Left Join as shown below
Let us see the Left Join report preview. From the below screenshot you can observe that, Left Join is producing 14 Rows which includes all the records from Employee table and matching records from Department table. Remember, 4 non matching records from Department table will be displayed as Nulls
Tableau Right Join
Let us change the Join type from Left Join to Right Join as shown below
Let us see the Right Join report preview. From the below screenshot you can observe that, Right Join is producing 12 Rows. Which includes all records from Department table and matching records from Employee table. Remember, 2 non matching records from Employee table will be displayed as Nulls
Tableau Full Outer Join
Let us change the Join type from Right Join to Full Outer Join as shown below
Let us see the Full Outer Join report preview. From the below screenshot you can observe that, Full Outer Join is producing 16 Rows. Which includes 2 Non matching records from Employee table, and 4 non matching records from Department table
NOTE: By this method, you can join more than two tables. Please be careful with complex joins, it will be difficult to understand the data.
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