Joins in Tableau
What is a join?
A join is performed to combine rows from two or more tables, based on a common column between them. This common column name either same or different doesn’t matter but their data types must be the same. Then only you can perform the join operation using two or more tables.
How does Tableau perform a join?
When it is required to perform complex analysis, Tableau joins data from multiple tables or multiple data sources. Based on need the for analysis there are different types of joins in Tableau.
There is another way Tableau combines data from multiple tables. This is called a Relationship. Relationships are flexible ways to combine data from multiple tables. When you create a relationship, you don’t need to define a join type as well as you won’t see a Venn diagram between the two tables. Relationships are dynamic whereas joins are the static way to combine data from multiple tables.
Features of Joins in Tableau:
1. They are displayed using Venn diagram icons between two tables.
2. Need to select join types and join clauses.
3. It will drop unmatched measure values.
4. Joined physical tables are merged into a single logical table.
Performing step–by–step join operation in Tableau:
Step-1: Load the data source to tableau public then double click on the first table named “Orders”.
Step-2: Then double click on the orders table, a thin blue line will appear on the left edge of the table.
Step-3: Then drag the People table to create a join with the orders table. It will show a Venn diagram join icon between the two tables.
Step-4: Then click on the Venn diagram icon, it will show the different types of joins that can be performed between the two tables. Then select the required join you want to perform based on your analysis. After that configure the join operation by adding a join operator and a field from the tables.
Step-5: when finished close the join canvas.
Types of Joins in Tableau:
1. Inner Join: When you perform an inner join to combine two tables, the result is a table that matches the values from both tables. If it doesn’t match then it is dropped entirely. Below is the icon of inner join.
2. Left Outer Join: When you perform a left outer join to combine two tables, the result is a table that contains all the values from the left table and corresponding values that match the right table. If a value in the left table doesn’t match the corresponding value in the right table, then it is padded with a null value.
3. Right Outer Join: When you perform a right outer join to combine two tables, the result is a table that contains all the values from the right table and corresponding values that match from the left table. If a value in the right table doesn’t match the corresponding value in the left table, then it is padded with a null value.
4. Full Outer Join: When you perform a full outer join to combine two tables, the result is a table that contains all the values from both the When a value from either table doesn’t have a match with the other table, then a null value is padded against that.
Thanks for reading!