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Outer Joins |
Introduction
An outer join is an operation that creates a list of records of two (or more) entities as follows:
Let’s consider the following list of departments of a company:
Let’s consider the following list of employees of a company:
The outer join operation is performed using the OUTER JOIN operator. It comes in various options, which precede the OUTER JOIN expression with a certain keyword:
SELECT Employees.EmployeeNumber, Employees.FirstName, Employees.LastName, Departments.Department, Employees.Title FROM Departments LEFT OUTER JOIN Employees ON Departments.Code = Employees.DepartmentCode;
This would produce:
SELECT Employees.EmployeeNumber, Employees.FirstName, Employees.LastName, Departments.Department, Employees.Title FROM Departments RIGHT OUTER JOIN Employees ON Departments.Code = Employees.DepartmentCode;
This would produce:
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