In general, there are four types of joins that you can use in Tableau: inner, left, right, and full outer. If you aren’t sure what join type you want to use to combine data from multiple tables, you should use relationships.
Tableau works the same as SQL. So, it supports all Joins possible in SQL
- Left Outer Join
- Right Outer Join
- Full Outer Join
- Inner Join
Tableau works the same as SQL. So, it supports all Joins possible in SQL
- Left Outer Join
- Right Outer Join
- Full Outer Join
- Inner Join
Types of SQL Joins
In Sql Server we have only three types of joins. Using these joins we fetch the data from multiple tables based on condition.
Inner join returns only those records/rows that match/exists in both the tables. Syntax for Inner Join is as
Select * from table_1 as t1 inner join table_2 as t2 on t1.IDcol=t2.IDcol
We have three types of Outer Join.
Left outer join returns all records/rows from left table and from right table returns only matched records. If there are no columns matching in the right table, it returns NULL values. Syntax for Left outer Join is as :
Select * from table_1 as t1 left outer join table_2 as t2 on t1.IDcol=t2.IDcol
Right outer join returns all records/rows from right table and from left table returns only matched records. If there are no columns matching in the left table, it returns NULL values. Syntax for right outer Join is as :
Select * from table_1 as t1 right outer join table_2 as t2 on t1.IDcol=t2.IDcol
Full outer join combines left outer join and right outer join. This join returns all records/rows from both the tables.If there are no columns matching in the both tables, it returns NULL values. Syntax for full outer Join is as :
Select * from table_1 as t1 full outer join table_2 as t2 on t1.IDcol=t2.IDcol
2. ## Cross Join
Cross join is a cartesian join means cartesian product of both the tables. This join does not need any condition to join two tables. This join returns records/rows that are multiplication of record number from both the tables means each row on left table will related to each row of right table. Syntax for right outer Join is as :
Select * from table_1 cross join table_2
Self join is used to join a database table to itself, particularly when the table has a Foreign key that references its own Primary Key. Basically we have only three types of joins : Inner join, Outer join and Cross join. We use any of these three JOINS to join a table to itself. Hence Self join is not a type of Sql join.
Join Examples
Suppose we following three tables and data in these three tables is shown in figure. You can download the SQL script used in this article by using link.
Inner Join
SELECT t1.OrderID, t0.ProductID, t0.Name, t0.UnitPrice, t1.Quantity, t1.Price FROM tblProduct AS t0 INNER JOIN tblOrder AS t1 ON t0.ProductID = t1.ProductID ORDER BY t1.OrderID
Inner Join among more than two tables
SELECT t1.OrderID, t0.ProductID, t0.Name, t0.UnitPrice, t1.Quantity, t1.Price, t2.Name AS Customer FROM tblProduct AS t0 INNER JOIN tblOrder AS t1 ON t0.ProductID = t1.ProductID INNER JOIN tblCustomer AS t2 ON t1.CustomerID = t2.CustID ORDER BY t1.OrderID
Inner Join on multiple conditions
SELECT t1.OrderID, t0.ProductID, t0.Name, t0.UnitPrice, t1.Quantity, t1.Price, t2.Name AS Customer FROM tblProduct AS t0 INNER JOIN tblOrder AS t1 ON t0.ProductID = t1.ProductID INNER JOIN tblCustomer AS t2 ON t1.CustomerID = t2.CustID AND t1.ContactNo = t2.ContactNo ORDER BY t1.OrderID
Left Outer Join
SELECT t1.OrderID AS OrderID , t0.ProductID , t0.Name , t0.UnitPrice , t1.Quantity AS Quantity , t1.Price AS Price FROM tblProduct AS t0 LEFT OUTER JOIN tblOrder AS t1 ON t0.ProductID = t1.ProductID ORDER BY t0.ProductID
Right Outer Join
SELECT t1.OrderID AS OrderID , t0.ProductID , t0.Name , t0.UnitPrice , t1.Quantity AS Quantity , t1.Price AS Price FROM tblProduct AS t0 RIGHT OUTER JOIN tblOrder AS t1 ON t0.ProductID = t1.ProductID ORDER BY t0.ProductID
Full Outer Join
SELECT t1.OrderID AS OrderID , t0.ProductID , t0.Name , t0.UnitPrice , t1.Quantity AS Quantity , t1.Price AS Price FROM tblProduct AS t0 FULL OUTER JOIN tblOrder AS t1 ON t0.ProductID = t1.ProductID ORDER BY t0.ProductID
Cross Join
SELECT t1.OrderID, t0.ProductID, t0.Name, t0.UnitPrice, t1.Quantity, t1.Price FROM tblProduct AS t0, tblOrder AS t1 ORDER BY t0.ProductID
Self Join
To understand Self Join, suppose we following two tables and data in these two tables is shown in figure.
CREATE TABLE emp ( id int NOT NULL primary key, name varchar(100) NULL, designation varchar(50) NULL, supid int foreign key references emp(id) ) – In this table we have a Foreign key supid that references its own Primary Key id. We use it for Self Join INSERT INTO emp(id,name,designation) VALUES(1,‘mohan’,‘Manger’) INSERT INTO emp(id,name,designation,supid) VALUES(2,‘raj kumar’,‘SE’,1) INSERT INTO emp(id,name,designation) VALUES(3,‘bipul kumar’,‘Manager’) INSERT INTO emp(id,name,designation,supid) VALUES(4,‘mrinal kumar’,‘SE’,2) INSERT INTO emp(id,name,designation,supid) VALUES(5,‘jitendra kumar’,‘SE’,2)
CREATE TABLE empinfo ( id int primary key, address varchar(50) NULL ) INSERT INTO empinfo(id,address) VALUES(1,‘Delhi’) INSERT INTO empinfo(id,address) VALUES(2,‘Noida’) INSERT INTO empinfo(id,address) VALUES(4,‘Gurgaon’) INSERT INTO empinfo(id,address) VALUES(6,‘Delhi’) INSERT INTO empinfo(id,address) VALUES(7,‘Noida’)
select e.id,e.name,e.supid as managerid, ei.name as managername from emp e left join emp ei on e.supid=ei.id; – outer keyword is optional