top-rated free essay

Database concepts

By v7secondsv Jul 30, 2014 586 Words

Assignments Requirements
1.Look up the definition of functional dependency. Can you find a good example? In relational database theory, a functional dependency is a constraint between two sets of attributes in a relation from a database. Cars

Suppose one is designing a system to track vehicles and the capacity of their engines. Each vehicle has a unique vehicle identification number (VIN). One would write VIN → Engine Capacity because it would be inappropriate for a vehicle's engine to have more than one capacity. (Assuming , in this case, that vehicles only have one engine.) Transversely, Engine Capacity → VIN is incorrect because there could be many vehicles with the same engine capacity. This functional dependency may suggest that the attribute Engine Capacity be placed in a relation with candidate key VIN. However, that may not always be appropriate. For example, if that functional dependency occurs as a result of the transitive functional dependencies VIN → Vehicl e Model and Vehicle Model → Engine Capacity then that would not result in a normalized relation.

2.Look up the definition of transitive dependency. Can you find a good example? In Database Management System, a transitive dependency is a functional dependency which holds by virtue of transitivity. A transitive dependency can occur only in a relation that has three or more attributes. Let A, B, and C designate three distinct attributes (or distinct collections of attributes) in the relation. Suppose all three of the following conditions hold: 1.A → B

2.It is not the case that B → A
3.B → C
Then the functional dependency A → C (which follows from 1 and 3 by the axiom of transitivity) is a transitive dependency. In database normalization, one of the important features of third normal form is that it excludes certain types of transitive dependencies. E.F. Codd, the inventor of the relational model, introduced the concepts of transitive dependence and third normal form in 1971.

A transitive dependency occurs in the following relation:
BookGenreAuthorAuthor Nationality
Twenty Thousand Leagues Under the Sea
Science Fiction
Jules Verne

Journey to the Center of the Earth
Science Fiction
Jules Verne
Leaves of Grass
Walt Whitman

Anna Karenina
Literary Fiction
Leo Tolstoy

A Confession
Religious Autobiography
Leo Tolstoy

3.Look up “denormalization” and provide information on why anyone would want to do it. In computing, denormalization is the process of attempting to optimize the read performance of a database by adding redundant data or by grouping data.[1][2] In some cases, denormalization is a means of addressing performance or scalability in relational database software. A denormalized data model is not the same as a data model that has not been normalized, and denormalization should only take place after a satisfactory level of normalization has taken place and that any required constraints and/or rules have been created to deal with the inherent anomalies in the design. For example, all the relations are in third normal form and any relations with join and multi-valued dependencies are handled appropriately.

Examples of denormalization techniques include:
Materialised views, which may implement the following: Storing the count of the "many" objects in a one-to-many relationship as an attribute of the "one" relation Adding attributes to a relation from another relation with which it will be joined

Star schemas, which are also known as fact-dimension models and have been extended to snowflake schemas Prebuilt summarisation or OLAP cubes

Denormalization techniques are often used to improve the scalability of Web applications.

Cite This Document

Related Documents

  • Database Technology

    ...DATABASE TECHNOLOGIES CLASS T.E. ( INFORMATION TECHNOLOGY) HOURS PER LECTURES : 04 WEEK TUTORIALS : -PRACTICALS : 02 HOURS EVALUATION THEORY 3 SYSTEM: PRACTICAL -ORAL -TERM WORK -- SEMESTER VI MARKS 100 -25 25 Objectives of the course: • This course aims to provide continuum to where the first course of databases left off. Design aspe...

    Read More
  • Database and Programming

    ...College of Business Hospitality & Tourism Studies Department of Computer Science & Information System CIN623 Database Design & Programming Final Examination Trimester 1 – 2011 Date: Duration:3 hours plus 10 minutes INSTRUCTION TO STUDENTS 1. You are allowed ten minutes extra reading time during which you are not to write 2. Write all answers t...

    Read More
  • Database Normalization and Logical Process Concept Paper

    ...Database Normalization and Logical Process Concept paper This short paper will explain with a simple example the process and the need of normalization in the most of the business databases. Complete proposal break down (Timeline phases, Financial phases) will be submitted per management request. Overview At first any database should be design...

    Read More
  • Database Normalization

    ...Normalization Normalization is a method for organizing data elements in a database into tables. Normalization Avoids • Duplication of Data – The same data is listed in multiple lines of the database • Insert Anomaly – A record about an entity cannot be inserted into the table without first inserting information about an...

    Read More
  • Tour Operator Agency Database

    ... Tour Operator Agency Database Jeremy Clark Dr. Larisa Bulysheva CIS 515 – Strategic Plan For Database Systems August 14, 2013 Tour Operator Agency Database Week 6 Assignment 5 Mike Jennings Enhanced Database Management Strategy Proposal An efficient data structure design requires a thorough a...

    Read More
  • Database Design Paper

    ...Database Design Paper “A database is a structured collection of records or data that is stored in a computer system. In order for a database to be truly functional, it must not only store large amounts of records well, but be accessed easily. In addition, new information and changes should also be fairly easy to input.” (; to e...

    Read More
  • What Is Database Normalization

    ...August 4, 2009 What is Database Normalization? Database Normalization is a systematic way of ensuring that a database structure is suitable for general – purpose quering and normalization is the process of efficently organizing data in a database. This process was first introduced in 1970 by E.F. Codd and has since been redefined to high...

    Read More
  • database marketing

    ...UPTREND VALUE : DATA BASE MARKETING In today’s competitive climate ,marketing and cutomer’s data have became the most important key of strategic competition for many firm. This advances in bussiness and marketing makes firms more sensitive for data with the efficacy of increasing role of information technologies in preparing marketing ...

    Read More

Discover the Best Free Essays on StudyMode

Conquer writer's block once and for all.

High Quality Essays

Our library contains thousands of carefully selected free research papers and essays.

Popular Topics

No matter the topic you're researching, chances are we have it covered.