what is self join in sql

1/* SELF JOIN - Joining a table with itself is called as self join.
2  It is classified under any type of join.
3  INNER JOIN
4  OUTER JOIN
5CROSS JOIN. */
6SELECT Column_List
7FROM Left_Table_Name AS Alias_Name
8JOIN_TYPE Right_Table_Name AS Alias_Name
9ON Alias_Name.Column_List [Operator] Alias_Name.Column_List
10
11/* Example*/
12SELECT E.Name AS Employee, M.Name AS Manager
13FROM tblEmployee E
14LEFT JOIN tblEmployee M
15ON E.ManagerID = M.EmployeeID

1SELECT
2    e.first_name + ' ' + e.last_name employee,
3    m.first_name + ' ' + m.last_name manager
4FROM
5    sales.staffs e
6INNER JOIN sales.staffs m ON m.staff_id = e.manager_id
7ORDER BY
8    manager;

1Self is joining a table to itself.
2
3-- assume employee table as 2 different table using different alias 
4-- as  manager and worker 
5-- we want to join these 2 virtual manager and worker table 
6-- to get manager's first name and worker's first name 
7-- our condition is worker's manager_id match managers employee id
8
9SELECT  manager.FIRST_NAME AS MANAGER_NAME , 
10        worker.FIRST_NAME AS WORKER_NAME 
11FROM EMPLOYEES manager 
12INNER JOIN EMPLOYEES worker on worker.MANAGER_ID = manager.EMPLOYEE_ID  
13
14order by 1 
15;