Unlike SQL INNER JOIN, SQL OUTER JOIN selects rows from 2 joined tables even there is no matches found.
There are three kind of SQL OUTER JOINs:
SQL LEFT OUTER JOIN
SQL RIGHT OUTER JOIN
SQL FULL OUTER JOIN
SQL OUTER JOIN Example
Table: Employees
EmployeeId | FirstName | LastName |
---|---|---|
203 | Aciyy | Uioiakk |
204 | Qiaiiua | Nikaiy |
205 | Iulada | Benooo |
206 | Wiaoooa | Yugh |
EmployeeId | |
---|---|
203 | AciyyU@mycomany.com |
204 | QiaiiuaN@mycomany.com |
205 | IuladaB@mycomany.com |
Select all the employees with Email address:
SELECT emp.EmployeeId, emp.FirstName, emp.LastName, Email.Email FROM Employees AS emp LEFT OUTER JOIN Email ON emp.EmployeeId = Email.EmployeeId
The result will look like:
EmployeeId | FirstName | LastName | |
---|---|---|---|
203 | Aciyy | Uioiakk | AciyyU@mycomany.com |
204 | Qiaiiua | Nikaiy | QiaiiuaN@mycomany.com |
205 | Iulada | Benooo | IuladaB@mycomany.com |
206 | Wiaoooa | Yugh |