GITTA-Logo
PDF Version of this document Search Help Glossary

Lesson Navigation IconRelationales Datenmodell

Unit Navigation IconKonzepte

Unit Navigation IconAbbildung ER-Schema

LO Navigation IconERM concepts

LO Navigation IconRule 1

LO Navigation IconRule 2

LO Navigation IconRule 3

LO Navigation IconRule 4

LO Navigation IconRule 5

LO Navigation IconRule 6

LO Navigation IconRule 7

LO Navigation IconRule 8

LO Navigation IconAnwendung der Regeln

LO Navigation IconUmwandlungsübung

Unit Navigation IconData integrity

Unit Navigation IconNormalisierung

Unit Navigation IconSummary

Unit Navigation IconRecommended Reading

Unit Navigation IconGlossary

Unit Navigation IconBibliography

Unit Navigation IconMetadata


GITTA/CartouCHe news:


Go to previous page Go to next page

Rule 8

If in rule 1 you find subclasses then transform them according to this rule.

Definition rule 8

Define a relational scheme R for the superclass C with the attributes A(R)=(K, A1, A2, .., An), where K is the primary key. For each subclass create a new relational scheme Ri with their attributes and the primary key K of superclass C as an additional attribute. The primary key of Si is also K.

In this example you can see the application of rule 8:

Rule 8a

Using the superclass define a relational scheme R with a primary key K:

Employee(ENumber)

For each subclass create a relational scheme:

Technician

Engineer(Training)

Add the primary key K of the superclass as attribute of the subclasses and use it also as primary key:

Employee(ENumber),

Technician(ENumber),

Engineer(ENumber, Training)

Top Go to previous page Go to next page