Understanding Entity Relationship Models

What is an entity in an entity relationship model?

• An entity is a method for data retrieval.

• An entity is a type of database table.

• An entity is a real-world object or concept in an entity-relationship model.

• An entity is a programming language construct.

Define an attribute in the context of an entity.

• An attribute is a property or characteristic of an entity.

• An attribute is a method used by an entity.

• An attribute is a synonym for an entity.

• An attribute is a type of entity.

What is the purpose of a relationship in an entity relationship model?

• To categorize entities into different types.

• To enforce data integrity rules.

• To establish primary keys for entities.

• To define associations between entities.

How do entities differ from attributes?

• Attributes are objects; entities are their properties.

• Entities are objects; attributes are their properties.

• Entities are always singular; attributes can be plural.

• Entities describe actions; attributes describe states.

What is a primary key in an entity?

• A primary key can be duplicated within an entity.

• A primary key is an optional identifier for a record.

• A primary key is a unique identifier for a record in an entity.

• A primary key is a type of foreign key.

Explain the concept of a foreign key.

• A foreign key is a field that contains only numeric values.

• A foreign key is a field in one table that links to the primary key of another table, establishing a relationship between the two.

• A foreign key is a unique identifier for a record in the same table.

• A foreign key is a type of index that speeds up database queries.

What is the significance of cardinality in relationships?

• Cardinality is solely about the quantity of data stored.

• Cardinality only applies to numerical data types.

• Cardinality is irrelevant in database design.

• Cardinality is significant as it defines the nature and constraints of relationships between entities.

Describe the difference between one-to-one and one-to-many relationships.

• In a one-to-one relationship, entities can share multiple connections; in a one-to-many relationship, each entity can only connect to one.

• In a one-to-one relationship, one entity can be associated with multiple entities; in a one-to-many relationship, each entity is paired with one and only one entity.

• A one-to-one relationship allows multiple entities to be linked to a single entity, while a one-to-many relationship restricts this.

• In a one-to-one relationship, each entity is paired with one and only one entity; in a one-to-many relationship, one entity can be associated with multiple entities.

What role do attributes play in defining an entity?

• Attributes are only used for visual representation of an entity.

• Attributes are irrelevant in the context of entity relationships.

• Attributes have no impact on the identity of an entity.

• Attributes are essential for defining the unique characteristics and properties of an entity.

How can relationships be represented visually in an ER diagram?

• Relationships are depicted using arrows pointing to the entities involved.

• Relationships are shown as rectangles with labels for each entity.

• Relationships are represented by circles indicating their strength.

• Relationships are represented by diamonds connecting entities with lines indicating their nature and cardinality.