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  SQL Server Tips by Gama and Naughter

Foreign Key

A foreign key enforces referential integrity by requiring that the values from a column either exist in a referenced table or are NULL. Relationships between tables are established by defining primary keys or unique keys and referencing them with foreign keys.

Example: To create a one to many relationship between Table1 and Table2. Table1_ID is the name of the column that is the primary key from Table1; Table2_f is the foreign key from Table2 that will relate both tables.

FK_Table2_Table1 FOREIGN KEY
) REFERENCES dbo.Table1

For a one to one relationship, both related columns must be primary keys. In this example, Table2_f should be a primary key or unique. A column can be a primary key and a foreign key simultaneously.

The above book excerpt is from:

Super SQL Server Systems
Turbocharge Database Performance with C++ External Procedures

ISBN: 0-9761573-2-2
Joseph Gama, P. J. Naughter  


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