SQL SELF JOIN

In this tutorial, we will learn how to use SELF JOIN using SQL.

SQL SELF JOIN

• SQL SELF JOIN is a join in which a table is joined with itself.
• You can not refer the same table more than one in a query, So table alias is used to assign different names to the table within a query.
• SQL SELF JOIN compares values of the same or different columns in the same table.

SELECT column(s)
FROM tableName1 T1,tableName1 T2
WHERE CONDITION;

Example:

Let us consider this table "Employee" for records.

Table Name: Employee

Example of SELF JOIN

This SQL statement matches employee that are from the same city, a query Will be:

SELECT A.EmpName AS EmpName1, B.EmpName AS EmpName2, A.City
FROM Employee A, Employee B
WHERE A.ID <> B.ID
AND A.City = B.City 
ORDER BY A.City;