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Can a PK be an FK as well ?

Posted on 2007-11-15
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Last Modified: 2008-03-23
Hello,

Can a PK be an FK as well ?

Thank you.
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Question by:matthew016
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by:steelseth12
steelseth12 earned 200 total points
ID: 20292600
foreign key of one table is the primary key of another table.
For the field to be the primary key of table A and the foreign key of table B ... No. Foreign key needs to take the values from table B.
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kiwi_nz earned 300 total points
ID: 20295410
yes a pk can be an fk - however this must be done in a special way. The trick is you must have two foreign keys that then composite into a Primary key - this is useful for when tables would otherwise have a many to many relationship you can put an intermediary table in between them and use the PK from each primary table as an FK in the intermediary table thereby creating a one to many - int table - many to one relationship.

Personally I dislike this method and always give the intemediary table a primary key and then add the two FK's thus making sure every single record in every single table is unique
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by:matthew016
ID: 21189650
The answer was just yes, no special way needed
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