Exam 4: Entity Relationship Ermodeling

Unary relationships are common in manufacturing industries.

The entity relationship diagram (ERD)represents the database as viewed by the end user.

In the entity relationship model,a table row corresponds to an entity instance.

A(n)attribute need not be physically stored within the database.

The entity relationship model uses the associative entity to represent a(n)relationship between two or more entities.

A weak relationship exists if the primary key of the related entity contains at least one primary key component of the parent entity.

Complex requirements may dictate data transformations,and they may expand the number of entities and attributes within the design.

The Chen notation identifies a weak entity by using a double-walled entity .

In Chen notation,there is no way to represent cardinality.

The Crow's Foot notation depicts the strong relationship with a(n)line between the entities.

The Crow's Foot notation is less implementation­oriented than the Chen notation.

Explain multivalued attributes with the help of examples.How are multivalued attributes indicated in the Chen Entity Relationship model?

To implement a small database,a database designer must know the "1" and the "M" sides of each relationship and whether the relationships are mandatory or optional.

Failure to understand the distinction between mandatory and optional in relationships might yield designs in which awkward (and unnecessary)temporary rows (entity instances)must be created just to accommodate the creation of required entities.

are characteristics of entities.

Identifying the attributes of entities helps in the better understanding of among entities.

Explain recursive relationships with the help of an example.

Software vendors have adopted the Chen representation because of its compact representation.

In Crow's Foot notation,an optional relationship between entities is shown by drawing a(n)on the side of the optional entity.

A composite identifier is a primary key composed of more than one attribute.