Question

In a referential integrity constraint where attribute A in relation R references attribute A in relation...

In a referential integrity constraint where attribute A in relation R references attribute A in relation S, what must be checked in each of these modifications for this referential integrity constraint. Be precise.

(a) inserting a tuple into relation R

(b) inserting a tuple into relation S

(c) deleting a tuple from relation R

(d) deleting a tuple from relation S

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Answer #1

All values of A in R should be present in S.

A)

Since we're inserting new tuples into R it should be present in S so we should check whether it's violating referential integrity constraint.

B)

Inserting into S doesn't cause any problem.

C)

Deleting a tuple in R doesn't cause any problem.

D)

Deleting a tuple in S may cause referential integrity constraint because if we delete the tuple to which an attribute is referring from R it can't find out the referred tuple.

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