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Lesson Navigation IconRelational database model

Unit Navigation IconConcepts

Unit Navigation IconTransforming ER-schema

Unit Navigation IconData integrity

Unit Navigation IconNormalization

Unit Navigation IconSummary

Unit Navigation IconRecommended Reading

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In a relational model real world objects are represented in tables. Each table is made out of rows and columns. Each row, also known as tuple or record, is made out of fields, also known as attributes. Each Attribute stands for a certain feature of the real world object. An attribute is defined by a name and its value.

Relations between tuples represent existing relationships between objects (tables). Furthermore key attributes have to be defined (usually displayed underlined in a relation). They are necessary for the allocation (relation) of objects (tables) and allow unique accesses to tables.

Integrity or consistency stands for the quality and reliability of data of a database system. A database is consistent if the data reflects the referenced objects correctly. It is inconsistent if there exist ambiguous or contradictory tuples, relations or tables in the database.

A relation model (scheme, entity) should reflect relationships that also logically (in the real world) belong together. To avoid anomalies different types of normalisations help keeping the database consistent.

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