Is441 Relational Data Model Exam 1

Front 1

REGULAR ENTITIES:
Transform each regular entity type into a ________________. The ________________ given to the relation is generally the same as that of the entity type. Each simple attribute of the entity type becomes an attribute of the relation. The identifier of the entity type becomes the _____________________________ of the corresponding relation.

Back 1

Relation, name, primary key

Front 2

Composite Attributes :

When a regular entity has a composite attribute, only the __________________ component attributes of the composite attribute are included in the new relation.

Back 2

simple

Front 3

Multivalued Attributes.

When the regular entity type contains a multivalued attribute, two new relations (rather than one) are created.
• The first relation contains all of the attributes of the entity type except the _______________________ attribute.
• The second relation contains _________ attributes that form its ___________________________. The first of two these attributes is the ___________________________ from the first relation, which becomes a ___________________ in the second relation. The second is the ________________________ attribute. The name of the second relation should capture the meaning of the multivalued attribute.

Back 3

multvalue,2, primary key, primary key, foreign key, multvalue.

Front 4

WEAK ENTITIES

Create a new relation and include in it all of the simple attributes (or simple components of composite attributes) as attributes of this relation. Then include the ____________________________________ of the ____________________________ relation as a ____________________________ attribute in this new relation. The primary key of the new relation is the _________________________ of this primary key of the identifying relation and the partial identifier of the ___________________ entity type.

Back 4

primary key, identifier, foreign key, combination, weak

Front 5

One-to-Many

Add the primary key attribute of the entity on the ___________ - side of the relationship as a foreign key in the relation that is on the ____________ - side of the relationship.

Back 5

one, many

Front 6

Many-to-Many

Add a new relation and include in it as ________________________________ attributes the _____________________________ for each of the two participating entity types. These attributes become the _________________________ of the new relation.

Back 6

primary key, foreign key, primary key

Front 7

One-to-One

Include in the relation on the optional side of the relationship the __________________________ of the entity type that has the _________________________ participation in the 1:1 relationship.

Back 7

primary key, mandatory

Front 8

ASSOCIATIVE ENTITIES

Use Default Identifier

The default primary key for the associative relation consists of the two ____________________ attributes from the other two relations. These attributes are then ________________________ that reference the other

Back 8

primary key, foreign key

Front 9

Add a Separate Identifier

Sometimes the data modeler will assign a separate identifier to the associative entity type on the E-R diagram. The main reasons for doing so are:
• the associative entity type has a natural _____________________________ that is familiar to end users and/or
• the default identifier (consisting of the identifiers for each of the participating entity types) may not _______________________ identify instances of the associative entity.

The process for mapping the associative entity in such a case is as follows:
1. The ____________________________ will be the identifier assigned on the E-R diagram.
2. The primary keys for the two participating entity types are then included as ___________________ in the associative relation.

Back 9

identifier, uniquely, surrogate key, foreign key.

Front 10

UNARY RELATIONSHIPS

One-to-Many

Add a _______________________________ attribute within the same relation that references the primary key values. (This foreign key must have the same ______________________ as the primary key.)

Back 10

foreign key, domain

Front 11

Many-to-Many

Create two relations: one to represent the entity type and an _______________________________ relation to represent the M:N relationship itself.

The primary key of the associative relation consists of two attributes. These attributes both take their values from the ___________________________ of the other relation. Any nonkey attribute of the relationship is included in the _________________________ relation.

Back 11

association, primary key, association