EER to Relational Mapping Rules

Vocabulary flashcards covering the relational representation and transformation rules for various Extended Entity-Relationship (EER) structures.

Regular entity (Relational Representation)

Create a relation with primary key and nonkey attributes.

Composite attribute (Relational Representation)

Each component of a composite attribute becomes a separate attribute in the target relation.

Multivalued attribute (Relational Representation)

Create a separate relation for multivalued attribute with composite primary key, including the primary key of the entity.

Weak entity (Relational Representation)

Create a relation with a composite primary key (which includes the primary key of the entity on which this entity depends) and nonkey attributes.

Binary or unary 1:M relationship (Relational Representation)

Place the primary key of the entity on the one side of the relationship as a foreign key in the relation for the entity on the many side.

Binary or unary M:N relationship or associative entity without its own key (Relational Representation)

Create a relation with a composite primary key using the primary keys of the related entities plus any nonkey attributes of the relationship or associative entity.

Binary or unary 1:1 relationship (Relational Representation)

Place the primary key of either entity in the relation for the other entity; if one side of the relationship is optional, place the foreign key of the entity on the mandatory side in the relation for the entity on the optional side.

Binary or unary M:N relationship or associative entity with its own key (Relational Representation)

Create a relation with the primary key associated with the associative entity plus any nonkey attributes of the associative entity and the primary keys of the related entities as foreign keys.

Ternary and n-ary relationships (Relational Representation)

Same as binary M:N relationships; without its own key, include as part of primary key of relation for the relationship or associative entity the primary keys from all related entities; with its own surrogate key, the primary keys of the associated entities are included as foreign keys in the relation for the relationship or associative entity.

Supertype/subtype relationship (Relational Representation)

Create a relation for the superclass, which contains the primary and all nonkey attributes in common with all subclasses, plus create a separate relation for each subclass with the same primary key (with the same or local name) but with only the nonkey attributes related to that subclass.