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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 are the various states through which a transaction passes through in its lifetime? Briefly discuss all the events that causes transition from one state to another. Ans:
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An example of a weak entity is Staff because the availabilityID cannot be uniquely identified unless it is used in conjunction with the foreign key known as availabilityID in the A
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Ask Write the SQL code that will create the table structure for a table named EMP _1. This table is a subset of the EMPLOYEE table. The basic EMP_1 table structure is summarized in
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