Question

The rule that a value of a foreign key must appear as a value of some specific table is called a

Answer 1

Answer:

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Explanation:

ANSWER.......

The rule that a value of a foreign key must appear as a value of some specific table is called a referential constraint. ( Referential integrity constraint is concerned with foreign key).

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Answer 2

Answer:

The rule that a value of a foreign key must appear as a value of some specific table is called a Referential Integrity.

Explanation:

• Referential Integrity constraint states that a tuple in one relation that refers to another relation must refer to an existing tuple in that relation.
• Referential integrity can be imposed in a Table using Foreign Key concept.
• Consider R1 and R2 are two tables . K1 is the Primary key of R1 and  K2 is the foreign key of R2 referencing K1. For this scenario  , it is required that for every tuple(row) t2 in R2 there must be a tuple(row) t1 in R1 such that t1[K1]=t2[K2].this is called referential integrity constraints.