A self-join is simply a normal SQL join that joins one table to itself.
This is accomplished by using table name aliases to give each instance of the table a separate name.
When Useful?Joining a table to itself can be useful when you want to compare values in a column to
other values in the same column.
We have sample records in
Inner Join Example----
Outer Join example---
This is accomplished by using table name aliases to give each instance of the table a separate name.
When Useful?Joining a table to itself can be useful when you want to compare values in a column to
other values in the same column.
We have sample records in
Employee table.Inner Join Example----
SELECT e1.Name EmployeeName, e2.name AS ManagerNameFROM Employee e1INNER JOIN Employee e2ON e1.ManagerID = e2.EmployeeIDOuter Join example---
SELECT e1.Name EmployeeName, ISNULL(e2.name, 'Top Manager') ASManagerNameFROM Employee e1LEFT JOIN Employee e2ON e1.ManagerID = e2.EmployeeID