SQL Self Join (Self-join)

SQL Self Join Description

A self-join is a regular join where a table is joined to itself.

Self Join Syntax

SELECT column_name(s)
FROM table1 T1, table1 T2
WHERE condition

T1 and T2 are different aliases for the same table.

Demonstration database

In this tutorial we will use the famous example database "Northwind".

Below is a sample from the table "Customers" ("Customers").

SQL Self Join Example

The following SQL statement selects customers from one city (City):

Run SQLSELECT A.CustomerName AS CustomerName1, B.CustomerName AS CustomerName2, A.City 
FROM Customers A, Customers B 
WHERE A.CustomerID <> B.CustomerID 
AND A.City = B.City 
ORDER BY A.City