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The Relational Database Design. ER- and EER-to-Relational Mapping. ER to Relational Mapping. Mapping of regular entity types Multivalued attributes Mapping of relationship Binary relationship N-ary relationship Mapping of weak entity types Mapping of specialization and generalization.

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the relational database design

The Relational Database Design

ER- and EER-to-Relational Mapping

er to relational mapping
ER to Relational Mapping
  • Mapping of regular entity types
  • Multivalued attributes
  • Mapping of relationship
    • Binary relationship
    • N-ary relationship
  • Mapping of weak entity types
  • Mapping of specialization and generalization
regular entity types
Regular Entity Types
  • Mapping
    • Create a new relation.
    • Include all the (simple) attributes of the entity.
    • Choose one of the key attribute as primary key.
multivalued attributes
Multivalued Attributes
  • Mapping
    • Create a new relation R for each multivalued A.
    • Include an attribute corresponding to A and the primary key attribute K (as a foreign key in R)
    • The primary key of R is K and A.
binary relationships
Binary Relationships
  • Binary M:N relationships
    • Create a new relation S.
    • Include as foreign keys the primary keys of the participating entities. The primary key of S is the combination of these.
    • Include all the (simple) attributes of the relationship type.
binary relationships1
Binary Relationships
  • Binary 1:1 relationships
    • Choose the entity with total participation.
    • Include the primary key of the other relation as a foreign key.
    • Include all the (simple) attributes of the relationship.
binary relationships2
Binary Relationships
  • Binary 1:N relationships
    • Choose the entity at the N side.
    • Include the primary key of the other relation as a foreign key.
    • Include all the (simple) attributes of the relationship.
n ary relationships
N-ary Relationships
  • Mapping
    • Create a new relation S.
    • Include as foreign keys the primary keys of the participating entities. The primary key of S is the combination of these.
    • Include all the (simple) attributes of the relationship type.
weak entity types
Weak Entity Types
  • Mapping
    • Create a relation.
    • Include all the (simple) attributes of the weak entity.
    • Include as a foreign key the primary key of the owner entity.
    • The primary key is the combination of the primary key of the owner and the partial key of the weak entity.
specialization and generalization
Specialization and Generalization
  • Mapping
    • Create a relation for the superclass (similar to mapping a regular entity)
    • Create a relation for each subclass, include primary key of the superclass (as its primary key) and local attributes.