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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.
What is a recursive relationship? Give an example not used in the text. A recursive relationship is a relationship among an entity and itself. For example, given the entity PER
Which are the two ways in which entities can participate in a relationship? Total and partial are the two ways in which entities can participate in a relationship
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The clause in SQL which specifies that the query result should be sorted in ascending or descending order based upon the values of one or much more columns is Ans : Order by
Can a domain, assigned to a data element be changed? Yes. We can do so by just overwriting the entry in the field domain.
Attributes and its types explain?
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