Modeling Data in the Organization Questions and Answers

Answer: B

Correct answer: False

A binary relationship is between exactly two entity types. Adding “or more” would cover ternary and higher relationships too and lose the distinction the term exists to make - the degree of a relationship is a precise count, not a lower bound.

Answer: D

Correct answer: Zero-to-Zero

Zero to zero is not a cardinality at all: a relationship in which no instance on either side ever participates is not a relationship. The three genuine forms are one-to-one, one-to-many and many-to-many, and a zero minimum is expressed as optional participation rather than as a maximum of zero.

Answer: B

Correct answer: False

A relationship can carry attributes of its own, and a many-to-many relationship usually must: the grade a student earned in a course belongs to neither the student nor the course but to the enrolment joining them. Such a relationship is generally converted to an associative entity to hold them.

Answer: C

Correct answer: One that is unique

Uniqueness is the one indispensable property: an identifier that does not distinguish instances identifies nothing. The others are the opposite of what is wanted - a good identifier does not change, is never null, and is unintelligent, carrying no meaning that might later need to change.

Answer: A

Correct answer: Attribute

The oval holds an attribute and is joined by a line to the entity or relationship it describes. Variants build on it - a double oval for a multivalued attribute, a dashed oval for a derived one, and an underlined name for the identifier.

Answer: B

Correct answer: False

An entity whose existence depends on another is a weak entity. A strong entity exists in its own right and has an identifier of its own. The statement has given the definition of one under the name of the other, which reverses the relationship it describes.

Answer: A

Correct answer: True

Notation captures structure, cardinality and identifiers; it does not capture rules such as a credit limit depending on a payment history, or an order not being shippable before a deposit clears. Those are recorded as text and implemented in constraints, triggers or application code - which is why the rules are documented alongside the model rather than only within it.

Answer: B

Correct answer: The resulting associative entity has an independent meaning.

The test is whether the association is itself something the business recognises and would name - a registration, a shipment, an assignment - rather than merely a link. Note that the first option is not sufficient as written: the conversion needs all the participating relationships to be many, not merely some.

Answer: C

Correct answer: Link between entities

A relationship is an association the organisation cares about between entity types, and it is drawn as a line joining them. A person, place or thing is an entity; a property of one is an attribute. Keeping the three straight is the whole of reading an entity-relationship diagram.

Answer: A

Correct answer: An attribute that can be broken into components

A composite attribute has meaningful parts - an address into street, town and postcode, a name into forename and surname. Whether to store it whole or in parts is a design decision: split it if the parts will be used separately, and leave it whole if it will always be handled as a unit.