ERDs Flashcards

1
Q

What is an Entity Relationship Diagram (ERD)?

A

An Entity Relationship Diagram (ERD) is a visual representation of the relationships between entities in a database.

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2
Q

What is an entity in an ERD?

A

An entity in an ERD represents a real-world object or concept, such as a person, place, or thing.

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3
Q

What is a relationship in an ERD?

A

A relationship in an ERD describes how entities are related to each other within a database.

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4
Q

What are the three main components of an ERD?

A

The three main components of an ERD are entities, attributes, and relationships.

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5
Q

True or False: An ERD is used to design the physical layout of a database.

A

False

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6
Q

What is cardinality in an ERD?

A

Cardinality in an ERD defines the maximum number of times an instance in one entity can be associated with instances in another entity.

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7
Q

What symbol is used to represent an entity in an ERD?

A

A rectangle

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8
Q

What symbol is used to represent a relationship in an ERD?

A

A diamond

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9
Q

What symbol is used to represent an attribute in an ERD?

A

An oval

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10
Q

What is a weak entity in an ERD?

A

A weak entity in an ERD does not have a primary key attribute of its own and relies on the relationship with another entity for identification.

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11
Q

What is a composite attribute in an ERD?

A

A composite attribute in an ERD is an attribute that can be divided into smaller, more basic attributes.

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12
Q

What is an associative entity in an ERD?

A

An associative entity in an ERD is an entity that exists to represent a many-to-many relationship between two other entities.

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13
Q

What is a recursive relationship in an ERD?

A

A recursive relationship in an ERD occurs when an entity is related to itself.

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14
Q

What is an ERD cardinality of ‘one-to-one’?

A

An ERD cardinality of ‘one-to-one’ means that each instance of one entity is associated with exactly one instance of another entity.

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15
Q

What is an ERD cardinality of ‘one-to-many’?

A

An ERD cardinality of ‘one-to-many’ means that each instance of one entity can be associated with multiple instances of another entity.

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16
Q

What is an ERD cardinality of ‘many-to-many’?

A

An ERD cardinality of ‘many-to-many’ means that each instance of one entity can be associated with multiple instances of another entity, and vice versa.

17
Q

What is an ERD crow’s foot notation used for?

A

ERD crow’s foot notation is used to represent cardinality in an ERD diagram.

18
Q

What is a subtype in an ERD?

A

A subtype in an ERD is a subset of entities that share common attributes or relationships distinct from other entities.

19
Q

What is a supertype in an ERD?

A

A supertype in an ERD is a generalized entity that contains common characteristics for a set of entities.

20
Q

What is an ERD attribute?

A

An ERD attribute is a property or characteristic of an entity that describes the entity.

21
Q

What is an ERD ternary relationship?

A

An ERD ternary relationship is a relationship between three entities.

22
Q

What is an ERD binary relationship?

A

An ERD binary relationship is a relationship between two entities.

23
Q

What is an ERD unary relationship?

A

An ERD unary relationship is a relationship within a single entity.

24
Q

What is an ERD attribute domain?

A

An ERD attribute domain is the set of allowable values for an attribute.

25
Q

What is an ERD key attribute?

A

An ERD key attribute is an attribute that uniquely identifies an entity within a database.