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Explain the concepts of relational data model?
Relational Data Model - The relational model was first introduced through Prof. E.F. Codd of the IBM Research in the year 1970 and attracted immediate attention because of its simplicity and mathematical foundation. The model uses the concept of a mathematical relation (such as a table of values) as its primary building block, and has its theoretical basis within set theory and first-order predicate logic. The relational model represents the database as a collection of relations. The relational model such as all other models consists of three basic elements:
Explain the Cascadeless Schedule A cascadeless schedule is one in which for every pair of transactions Ti and Tj like that Tj reads a data item before written by Ti, the commit
What is relationship? Give examples A relationship is an association between several entities. Example: A depositor relationship associates a customer with every account tha
What is the difference between SQL Server 2000 clustered and nonclustered indexes? With a clustered index, the data are kept in the bottom level of the index and in the similar
Explain the Attribute inheritance Ans: Throughout the rendering of the objects in a view, attribute sets of objects higher in the view hierarchy are inherited via objects below
What is NULL? Simply NULL means not in value.
How does the system cope up with a record crash when recovery is going on after the first crash? Ans: In a system the undo and redo operations are needed to be idempotent to c
write-set(T): Each data items that are written by a transaction T
Consider a database application that deals with an Employee relation with information such as SIN, name, data of birth (DOB), and DID (the ID of the department at which the employe
how many hourse have been spent on a certain project
Define the notation for classes and atrributes The notation for class, attribute, and operations are shown below: Figure: Class with attributes and operations A
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