Relationships?? Primary and Foreign Key

[natemclain]

Can someone explain how you can tell the difference in a Primary Key & Foreign Key?? I was looking at the Northwind DB and noticed that the Order Details Table had 2 Primary Keys. But I don't understand how you can tell the difference in the two?? Also, how can you setup multiple Primary Keys on 1 table? Can that be done? SO you can tie a Part Number and a AutoNumber to the same part so that duplication doesn't happen?

Thanks for the ongoing help!

natemclain

 

[Databaseguy]

A primary key is any feild, or combination of fields, that uniqely identifies each individual record in a table.

A foreign key is a key that's stored in , that points to the primary key in another table.

tblCust
Cust ID Name
(Primary key)
1 Microsoft
1 Microsoft

tblContact
ContactID Cust ID Name
(Primary key) (Foreign key)
1 1 Bill Gates
2 1 Fred Flintstone

A query could then pull up:
Cust ID Contact ID Custame Contact Name
1 1 Microsoft Bill Gates
1 2 Microsoft Fred Flintstone


Tyrone Lumley
augerinn@gte.net

http://server47.hypermart.net/databaseguy