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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.
Components of database manager The above functions are reached by the database manager. The major elements of a database manager are: Authorisation control: This mod
What is a query tree? Ans: A query tree, as well known as operator graph, is a tree data structure that corresponds to a relational algebra expression. It denotes the inpu
Define DBA database administrator? DBA : A database administrator (DBA) is a person who is responsible for the environmental aspects of a database. In common, these involves:
I have been given 8 differebt data warehouseing failure case studies. I need to question 4 questions for each
Which sorting technique is used to sort databases, whose sizes are very big? Give one such algorithm. Why do sorting techniques like quicksort, insertion sort, etc. not applied
You are working for the ABC Telecom and are given some customer records for data mining. You are asked to discover, from the data, patterns that characterize low-, medium- and high
What subschema expresses ? A subschema expresses the external view. (External schemas are called also called as subschemas)
Q. Explain the terms key constraints participation constraints and mapping caradinalities in ER model. Participation Constraints : The participation of an entity set E i
Can we delete data element, which is being used by table fields. No we cant delete data element.
wrie a report on whether a BSc n information systems develops the skills required by employers in Database administration
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