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A Relation Schema represented by R(A1, A2, ..., An) is made up of the relation name the list of attributes and R Ai that it contains. A relation is described as a set of tuples. Let r be the relation which have set tuples (t1, t2, t3, ..., tn). Each tuple is an ordered list of n-values t=(v1,v2, ..., vn).
The purpose of the relational model is to give a declarative function for specifying queries and data: users directly state what information the database have and what information they want from it, and let the database management system software take care of explain data structures for retrieval procedures and storing the data for answering queries.
It defines that no primary key value can be null. This is as the primary key is used to recognize individual tuple in the relation. So we will not be able to recognize the records
Data Fragmentation "Fragmentation includes decomposing the data in relation to non-overlapping component relations". Why do we require fragmenting a relation?
Set Difference If R1 and R2 are two union compatible relations or relations then result of R3 =R1- R2 is the relation that have only those tuples that are in R1 but not in R2.
Where does view definition stored? A view definition is permanently stored as part of the database.
What is called an evaluation primitive? A relational algebra operation annotated with instructions on how to evaluate is known as an evaluation primitive.
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Rearrange Classes and Operations Sometimes, the similar operation is defined across different classes and can easily be inherited from a familiar ancestor, but more often oper
Write short notes on domain relational calculus The domain relational calculus uses domain variables that take on values from an attribute domain rather than values for whole t
Benefits: It limits data access. It makes difficult queries look easy. It permits data independence. It presents dissimilar views of the similar data.
Databases and data warehouses both are databases and both contains number of rows and columns of tables containing data. Data warehouse is really different from databases because d
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