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It defines that the tuple in one relation that refers to another relation must refer to an existing tuple in that relation. This constraint is states on two relations (not essentially distinct). It uses a concept of foreign key and has been dealt with in more factors in the next unit.
Example
In the example given above, the value of C^ in every R tuple is matching with the value of C# in some S tuple. If a tuple has values (A6, B2, and C4) is added then it is invalid as referenced relation S doesn't contain C4. Therefore, it will be a violation of referential integrity constraint.
Differentiate sub-class and super-class? The specialization of a class is known as subclasses.eg: employee is a subclass of person and teller is a subclass of employee. Convers
Benefits and limitations
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What is meant by buffer blocks and disk buffer The blocks residing temporarily in main memory are referred to as buffer blocks. The area of memory where blocks reside t
Define what Immediate database modification technique uses? Ans: Both undo and redo.
What is Specialization? Specialization: Specialization permits you to describe new types of information (new structural types or latest domains of information), although reusin
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