Call now: (800) 766-1884  



 Home


 SQL Server Tips
 SQL Server Training

 SQL Server Consulting
 SQL Server Support
 SQL Server Remote DBA



 Articles
 Services
 SQL Server Scripts
 Scripts Menu



 

 

 

   
  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.

ALTER TABLE dbo.Table2 ADD CONSTRAINT
FK_Table2_Table1 FOREIGN KEY
(
Table2_f
) REFERENCES dbo.Table1
(
Table1_ID
)


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

 http://www.rampant-books.com/book_2005_2_sql_server_external_procedures.htm  

 

Burleson Consulting Remote DB Administration


 

 


 

 

 

 

 
Burleson is the America's Team

Note: The pages on this site were created as a support and training reference for use by our staff of DBA consultants.  If you find it confusing, please exit this page.

Errata?  SQL Server technology is changing and we strive to update our SQL Server support information.  If you find an error or have a suggestion for improving our content, we would appreciate your feedback.  Just  e-mail:and include the URL for the page.
 


Burleson Consulting
SQL Server database support

 

Copyright 1996 -  2013 by Vaaltech Web Services. All rights reserved.

Hit Counter