A FOREIGN KEY is a field or collection of fields in one table that refers to the PRIMARY KEY in another table. The table containing a foreign key is called the Child Table while the table which contains the Primary Key (or the Candidate Key) is known as the Referenced Table or the Parent Table.

Foreign keys are used to enforce referential integrity within our SQL Server database. For better understanding of the concept of foreign keys, we are using a GUI in SQL Server in this video tutorial. We will start with the basics; i.e., how to create a Foreign Key in a child table referencing its parent table.