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Lesson Navigation IconRelationales Datenmodell

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Unit Navigation IconAbbildung ER-Schema

Unit Navigation IconData integrity

LO Navigation IconSchlüsselintegrität

LO Navigation IconGegenstandsintegrität

LO Navigation IconReferentielle Integrität

LO Navigation IconIntegritätsgefährdung

Unit Navigation IconNormalisierung

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Entity integrity

The entity integrity is a result of the key integrity: No primary key is allowed to be the NULL(=no value). If NULL-values would be allowed for primary keys, than two tuples could have NULL as key value and therefore could not be distinguishably anymore. The key integrity would not be respected. In SQL special routines (unique, not null) are used for key and entity integrity.

Example:

ID Name Surname Year
NULL Miller John 1955
NULL Miller John 1985

Since the primary key (here ID) of both tuples is NULL, we are not able to distinct these tuples.

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