A rectangle represents which of the following in an ERD?
Answer: B
Correct answer: Entity
The rectangle is the entity symbol. The three shapes to know are rectangle for entity, oval for attribute and diamond for relationship; cardinality and optionality are shown by marks on the relationship lines rather than by shapes of their own.
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A binary relationship is a relationship between two or more entities.
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.
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A binary relationship cannot be which of the following?
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.
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Relationships cannot have attributes.
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.
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A good identifier is which of the following?
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.
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An oval represents which of the following in an ERD?
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.
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A strong entity is an entity whose existence depends on some other entity type.
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.
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Some business rules cannot be represented in common data modeling notation.
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.
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Which of the following conditions should exist if you want to convert a relationship to an associative entity?
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.
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A relationship is which of the following?
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.
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