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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.
What is aggregate function? Briefly describe it? Aggregate functions are functions that take a collection of values as input and return a one value. SQL offers 5 built-in aggre
The Internal or Physical Level The collection of files permanently stored on secondary storage devices is called as the physical database. The internal or physical level is t
An example of a weak entity is Staff because the availabilityID cannot be uniquely identified unless it is used in conjunction with the foreign key known as availabilityID in the A
Explain the Fundamental concepts of object-orientation Software developers, data base administrators (DBAs) need to be familiar with fundamental concepts of object-orientation.
What was the method in which records are physically stored in a specified order according to a key field in each record ? A method in which records are physically stored within
Explain the θ-join and equijoin Refer tables Car and Boat which list models of cars and boats and their relevant prices. Assume a customer wants to buy a car and a boat, but sh
Law Associates is a large legal practice based in Sydney. You have been asked to design a data model for the practice based upon the following specification: The practice emplo
Define two-phase locking protocol. Ans: Two-phase locking is significance in the context of ensuring that schedules are serializable. The two-phase locking protocol defines a p
Explain degree of relation? Degree of a Relation - The degree or arity of a relation is the number of attributes n of its relation schema.
Explain the cartesian product in Database Management System
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