Entity Relationship Diagram Concepts
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Entity Relationship Diagram Concepts

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Questions and Answers

Which attribute classification must always have a value for every instance associated with it?

  • Optional Attribute
  • Derived Attribute
  • Composite Attribute
  • Required Attribute (correct)

    • What distinguishes composite attributes from simple attributes?

  • Composite attributes have meaningful component parts. (correct)
  • Composite attributes cannot have parts.
  • Composite attributes are derived from other attributes.
  • Composite attributes are always single-valued.

    • Which of the following is an example of a multivalued attribute?

  • A person's name
  • A person's birth date
  • A person's mailing address
  • A person's phone numbers (correct)

    • Which of the following describes derived attributes?

    <p>Attributes that depend on other attributes for their value.</p> Signup and view all the answers

    What type of attribute allows for an instance to have zero or more values?

    <p>Optional Attribute</p> Signup and view all the answers

    What are the three main constructs used in an Entity Relationship (ER) Diagram?

    <p>Data entities, Relationships, Attributes</p> Signup and view all the answers

    Which of the following best describes a data entity in an ER Diagram?

    <p>A person, place, object, event, or concept</p> Signup and view all the answers

    In the context of ER Diagrams, what does an attribute represent?

    <p>A named property or characteristic of an entity</p> Signup and view all the answers

    What is the primary purpose of relationships in an ER Diagram?

    <p>To show associations between instances of entity types</p> Signup and view all the answers

    Which model is commonly used in the notation of ER Diagrams?

    <p>Chen Model and Crow’s Foot Model</p> Signup and view all the answers

    What does the term 'association' refer to in an ER Diagram?

    <p>A typed link between different entity instances</p> Signup and view all the answers

    What component of an ER diagram serves as a connector between entities?

    <p>Verb Phrase</p> Signup and view all the answers

    What does a Crow’s Foot notation represent in an ER Diagram?

    <p>The cardinality of entity relationships</p> Signup and view all the answers

    What is the purpose of a time stamp in data management?

    <p>To indicate when an event occurred that affected the data value</p> Signup and view all the answers

    What distinguishes multivalued attributes from derived attributes?

    <p>Multivalued attributes can take on more than one value for an instance.</p> Signup and view all the answers

    What characteristic does the time stamp attribute exhibit?

    <p>It is both multivalued and composite.</p> Signup and view all the answers

    Which of the following statements about identifiers is true?

    <p>Identifiers should never be null and should remain constant.</p> Signup and view all the answers

    Why is modeling time-dependent data considered important?

    <p>It is influenced by regulations like HIPAA and Sarbanes-Oxley.</p> Signup and view all the answers

    In an E-R diagram with an associative entity, what does it primarily indicate?

    <p>The date range of a product's assignment to a particular product line.</p> Signup and view all the answers

    When choosing identifiers, which of the following criteria should be avoided?

    <p>Intelligent identifiers containing changeable information.</p> Signup and view all the answers

    What is a derived attribute?

    <p>An attribute calculated from related attribute values.</p> Signup and view all the answers

    What is meant by cardinality constraints in a ternary relationship?

    <p>They determine the number of entities involved in the relationship.</p> Signup and view all the answers

    Which of the following is an example of a multivalued attribute?

    <p>An employee's skill set.</p> Signup and view all the answers

    Which type of identifier is characterized by being a combination of multiple attributes?

    <p>Composite Identifier.</p> Signup and view all the answers

    What is the primary advantage of using simple keys instead of long composite keys for identifiers?

    <p>Simple keys are less likely to change.</p> Signup and view all the answers

    Why should identifiers ideally not contain intelligent identifiers?

    <p>They often lead to confusion and are less flexible.</p> Signup and view all the answers

    What term describes the number of entity types that participate in a relationship?

    <p>Degree of Relationships</p> Signup and view all the answers

    Which relationship type involves only one entity related to itself?

    <p>Unary Relationship</p> Signup and view all the answers

    In a one-to-many relationship, how many entities can be related on the 'one' side?

    <p>One entity can relate to many others</p> Signup and view all the answers

    What type of relationship is characterized by each entity on one side being related to many entities on the other side, and vice versa?

    <p>Many-to-Many</p> Signup and view all the answers

    Which of the following is NOT a degree of relationship?

    <p>Tertiary</p> Signup and view all the answers

    What is the key characteristic of a binary relationship?

    <p>Involves two different entity types</p> Signup and view all the answers

    Which relationship can have attributes of its own?

    <p>All Relationship Types</p> Signup and view all the answers

    In cardinality terminology, which statement is TRUE regarding a one-to-one relationship?

    <p>Exactly one entity is related to another.</p> Signup and view all the answers

    Study Notes

    Entity Relationship (ER) Diagram

    • Represents entities, associations, and data elements for an organization.
    • Composed of three main constructs: Data entities, Relationships, Attributes.
    • Two commonly used notation models: Chen Model and Crow's Foot Model.

    Key Constructs in ER Diagrams

    • Entity: A real-world person, place, object, event, or concept about which data is maintained.
    • Relationship: Association between instances of two or more entity types.
    • Attributes: Properties or characteristics of an entity or relationship.

    Attributes Classifications

    • Required vs. Optional Attributes: Required must have a value; optional may not have a value.
    • Simple vs. Composite Attribute: Composite has meaningful components (e.g., address).
    • Single-Valued vs. Multivalued Attribute: Multivalued can have more than one value (e.g., multiple skills).
    • Stored vs. Derived Attributes: Derived values are calculated from related attributes, not physically stored.

    Identifiers (Keys)

    • Identifier: Attribute or combination of attributes that uniquely identifies instances of an entity type.
    • Candidate Identifier: An attribute that meets the criteria to function as a key.
    • Criteria for identifiers include stability (value won't change) and non-null properties.

    Degree of Relationships

    • Unary Relationship: One entity relates to itself.
    • Binary Relationship: Two different entity types relate.
    • Ternary Relationship: Three different entity types relate.

    Cardinality of Relationships

    • One-to-One: Each entity has exactly one related entity.
    • One-to-Many: One entity can relate to many, while the other relates to one.
    • Many-to-Many: Entities on both sides can relate to many on the other side.

    Relationship Examples

    • Unary relationships link one entity type to itself.
    • Binary relationships connect two different entity types.
    • Ternary relationships involve connections among three different entity types.

    Additional Concepts

    • Time-stamping: A time value associated with data indicating when events occurred.
    • Example of composite and multivalued attribute: Price History can contain multiple values and components.
    • Importance of modeling time-dependent data due to regulations like HIPAA and Sarbanes-Oxley.

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    Related Documents

    Chapter 3 - Data Modeling (1).pdf

    Description

    This quiz covers the fundamental concepts of Entity Relationship (ER) Diagrams, focusing on the logical representation of entities, relationships, and data elements used in organizations. It also highlights the notation methods, such as the Chen Model and Crow's Foot notation. Test your knowledge on the key constructs and their applications in business data modeling.

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