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#1 rnty  Icon User is offline

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Referential integrity constraint

Posted 12 October 2014 - 09:10 AM

Suppose (A, B ) and (C,D) are two relation schemas. Let r1 and r2 be the corresponding relation instances. B is a foreign key that refers to C in r2. If data in r1 and r2 satisfy referential integrity constraints, what is ALWAYS TRUE?

My Ans
FK data - PK data = {}

Given Ans
FK data - PK data = {}
PK data - FK data != {}

I dont understand how PK data - FK data != {}.
Also, what are the conditions to be satisfied if referential integrity constraint exists.

Thanks in advance

This post has been edited by rnty: 12 October 2014 - 09:15 AM


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