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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.
Rules Of Data Normalisation Let us now summarise Normalisation with the help of various clean rules. The following are the necessary rules for the Normalisation process: 1.
Multilevel Indexing Scheme Consider the indexing scheme where the address of the block is consider in the index for each record, for a little file, this index would be little a
Explain the relevance of Data Dictionary in a Database System? Data dictionary is a database in its own right residing on the disk that consist of Meta data which is = Data abo
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What is system catalog or catalog relation? How is better known as? A RDBMS maintains a explanation of all the data that it contains, information about every relation and index
Define seek time. The time for repositioning the arm is known as the seek time and it enhances with the distance that the arm is known as the seek time.
Which is another name for weak entity? Child is another name of weak entity.
Describe the algorithm to draw the dependency graph? Ans: Algorithm to draw Precedence Graph is like this: a. For every transaction T i participating in schedule S, make
exercise solution
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