LIBRIS titelinformation: Databasteknik / Thomas Padron-McCarthy, Tore Risch. 6 Oct DATABASTEKNIK (database technology) – 1MB Fall , UU logo. NEWS. – Exam results from the exam can be found. 6 Oct Här hittar ni kursinformation och kursmaterial för kursen Databasteknik – 1DL KURSLITTERATUR. Elmasri & Navathe: Fundamentals of.

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An owner of a car is either a company or a person, not all persons own cars, but all company owns cars Such subclass is called category.


It is showen by double straight line in ER diagram. Open Preview See a Problem? They all are an employee of the company, have attributes, PN, name, and so on. Generalization is a reverse process of specialization— process of identifying common features among several entity types.

Databasteknik (VT-16)

If you wish to download it, please recommend it to your friends in any social system. Departure and destination addresses together with times should also be recorded. Anton Larsson rated it liked it Mar 15, Navathe Slide 1. A taxi may be picked on a street or ordered though an operator who assigns the order to a certain driver and a car.


databsateknik Johan Gudmundsson marked it as to-read Jan 28, An entity can not exist in the database only by being a member of subclass. A database represents some aspect of eatabasteknik real world, i. Some part of the real world about which data is stored in a database. Subclass inherits all the attributes of the entity of the superclasses, and also inherits all the relationships in which the superclass participates.

M, meaning that each owner can owns any number of car, and a car can be related to any number of owner.

An each entity has attributes. For example, we have such data requirement … ER model is not able to model these requirments.

LIBRIS – Databasteknik /

Model defines concepts that can be used to define a particular domain ER model: Exercise 1 Both disks and main memory support direct access to any desired location page. Subclass may have specific attributes.

The attributes describe an entity. Goodreads helps you keep track of books you want to read. They have PN and name.

The conceptual model actually has nothing at all to do with computers, since it is just a description of the world, which could equally well be used e.


So a shared subclass inherits attributes and relationships from multiple superclasses. A total category holds the union of all entities in its superclasses.

Such a subclass is called shared subclass. Databastekmik by Liliana Lazenby Modified over 4 years ago. Peter Nilsson rated it liked it Jan 01, Subclasses are attached by lines to a circle.

Blocks needed for databasteonik file: My presentations Profile Feedback Log out. Moreover, record removal implies waste of space.

On average, main memory accesses. Databasteknik by Thomas Padron-Mccarthy. Multivalued — attributes can have a number of values for an entity.

For example, student grades and transcripts at a university. May not be convenient if the types have to be extended by the user.

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