Dim/Fac Vs FK/PK

What is the basic difference between Dimension/Facts relationship and PK/FK realtionships?

Thanks
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anushahannaAsked:
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dportasCommented:
Is this a homework question? I'm not sure I understand the question. Usually a dimension table is the "parent" (the referenced table) of a foreign key constraint on the fact table (referencing table).
anushahannaAuthor Commented:
dportas,

I'm working with a OLAP DB and hence the question to get a clarification.

sorry i should have been more clear in the quesiton: in OLAP we use PK/FK between Dim and Fact tables. In OLTP we use the same between normalized tables.

Is there anything specific about the PK/FK in the 2 models that are different? Or the PK/FK is not dependent on the model (OLAP/OLTP)..

Thanks
dportasCommented:
No difference that I can think of.

OLAP doesn't necessarily imply "dimensional". If by "OLAP" you just mean a database used for business intelligence / decision support purposes then that could also be a normal form model. But either way a foreign key means the same thing in each case.

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anushahannaAuthor Commented:
Thanks for the clarification.

yes, by OLAP i mean reporting/decision support database. Thanks for the point that OLTP can be used for the same, too.

By "dimensional", you mean Facts/Dimension table concept, right?
dportasCommented:
>> By "dimensional", you mean Facts/Dimension table concept, right?

Yes I mean the "Dimensional Model" popularised by Ralph Kimball in the 1990s. In my view it's just a rather limited, inflexible and now outdated hotch potch of design patterns. Normal form is generally a much more useful way to design a data warehouse. Normal form was of course always the recommendation of Bill Inmon, who invented the term data warehouse in the first place.
anushahannaAuthor Commented:
dportas, thanks for the helpful answer and guidance and also that small piece of history.

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