SQL SELF JOIN

SQL SELF JOIN is a normal join which joins a table to itself.

Note: SQL SELF JOIN can be any kind of joins: SQL INNER JOIN, SQL LEFT JOIN, SQL RIGHT JOIN, SQL FULL JOIN. And that SQL SELF JOIN itself is not an SQL keyword.

SQL SELF JOIN Syntax

SELECT a.Column1, a.Column2, ... , b.Column3, b.Column4, ...
FROM Table1 a
INNER JOIN Table1 b
ON a.Column1 = b.Column2

SQL SELF JOIN Example

Table: Employees

Select all the employees and his/her manager, if has any:

SELECT a.FirstName
           , a.LastName
           , b.LastName AS Manager
FROM Employees a
LEFT JOIN Employees b
ON a.ManagerID = b.EmployeeId

The result will look like:

Select all the employees at the same department with Mazojys Fxoj:

SELECT a.FirstName
           , a.LastName
           , a.Department
FROM Employees a
INNER JOIN Employees b
ON a.Department= b.Department
WHERE b.FirstName = 'Mazojys' AND b.LastName = 'Fxoj'

The result will look like: