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Explain the concept of a data model ?
Data Model - Model is an abstraction procedure which hides irrelevant details although highlighting details relevant to the applications at hand. As same, a data model is a collection of concepts which can be used to elaborate structure of a database and gives the essential means to achieve this abstraction. Structure of database means the data types, relationships, and constraints which should hold for the data. In common a data model consists of two elements:
• A mathematical notation for expressing relationships and data.• Operations on the data which serve to express queries and other manipulations of the data.
Timestamps For Read operations: If TS (T) If TS (T) >= W-timestamp (Q), then the transaction T is trying to read a value of data item Q which has been written and committed
Backward Recovery (UNDO): In this system the uncommitted changes made by a transaction to a database are undone. Instead the system is reset to the last consistent state of databa
Example - ALTER TABLE emp MODIFY (empno NUMBER (7));
Mention the several levels in security measures. A) Database system B) Operating system C) Network D) Physical Human
Identify the need and use of data control through problem solving, illustration
Illustrate the view of software architecture A model is a semantically closed abstraction of system composes of elements. It can be visualized using any of the following five v
Consider the subsequent relations RENTER(rno, fname, lname, address, tel_no, pref_type, max_rent) VIEWING(rno, pno, date, comment) PROPERTY_FOR_RENT( pno, street, area ,city,
The natural join is equal to which product? The natural join is equal to Combination of projection and Cartesian product
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What exactly is the concept of Functional Dependencies? And how do we associate this concept with the logic of Super-keys, Candidate Keys, etc? Given Relation R(A,B,C,D,E) with de
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