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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.
WHY SHOULD NULL IN A RELATION BE AVOID AS possible?
What are the requirements to ensure the objectives of file management principle is realized?
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Increases efficiency : Data is stored close to most often used site, therefore retrieval would be faster. Also, data that is not required by local applications is not stored, there
i would like to ask if you will do assignment of database number of words 1500 and how much
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