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Introduction to Joins In Tableau

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by Saikumar
Last modified: September 18th 2020

Join is a query that combines the data from 2 or more tables, sheets, files in a single datasource based on the join condition

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Rules to perform Join:
To perform Join we are having two rules
1) Both the tables should have a common column
2) Based on the common data type in the both tablesJoin Types:
Depending on the join condition. Joins are divided into two types 
1) Equi Joins
2) Non-Equi Joins
Equi Joins: In the Join condition if you use the equality operator (“=”) then such a kind of Join is called as “ Equi Join”
Non-Equi Joins: In the Join condition apart from the equality if we use any operator like <,>,<>,<=,>= etc.
Suck kind of join is known as “Non-equi Join”
Equi Join Types:
Equi Join is divided into 3 types
1. Inner Join
2. Outer Join
3. Self Join
Again outer join is divided into 3 different types
1. Left Outer
2. Right Outer
3. Full Outer
Inner Join: 
Inner Join combines the data from two tables and it display only the matching records (or) common records.

Join Condition: Table1.ID=Table2.ID

Table 1:

Name ID
Ramesh 1
Ravi 2
Praveen 3
Kiran 4

Table 2:

ID Designtion
1 Professor
2 Professor
3 Professor
4 Principal

Output:

Name Designation
Ramesh Professor
Ravi Professor
Praveen Professor


Outer Join
Left Outer Join: 
Is is display the complete data from the left table and matching records from the the Right Table.

Table1.ID=Table2.ID(+)

Following Above Table 1 & Table 2

Output:

Name Designation
Ravi Professor
Ramesh Professor
Praveen Professor
Kiran Null

Right Outer Join: 
It is display complete data from right table and matching records from left table.

Table1.ID(+)=Table2.ID

Following Above Table 1 & Table 2

Output:

Name Designation
Ramesh Professor
Ravi Professor
Praveen Profess
Null Principal

Full Outer Join: 
It displays the complete data from both the tables

Full Outer Join

Following Above Table 1 & Table 2

Output:

Name Designation
Ramesh Professor
Ravi Professor
Praveen Professor
Kiran Null
Null Principla

Self Join: 
Performing a join to the same table itself is known as “Self Join”

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About Author

author
NameSaikumar
Author Bio

As a Senior Writer for Mindmajix, Saikumar has a great understanding of today’s data-driven environment, which includes key aspects such as Business Intelligence and data management. He manages the task of creating great content in the areas of Programming, Microsoft Power BI, Tableau, Oracle BI, Cognos, and Alteryx. Connect with him on LinkedIn and Twitter.