Database Concepts Lecture 3
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Questions and Answers

Which characteristic best describes referential integrity?

  • A foreign key can exist without a corresponding primary key.
  • A foreign key must have a matching primary key or be null. (correct)
  • A foreign key is only relevant in a single table.
  • A foreign key must always have a valid form.

    • In the context of a database, what does the term 'conceptual ERD' refer to?

  • A model with the least detail used for high-level understanding. (correct)
  • A detailed representation of entities, attributes, and relationships.
  • A blueprint that shows specific database column types.
  • An ERD that includes foreign and primary key definitions.

    • Why cannot 'Phone' be a primary key in the EMPLOYEE table?

  • It has too many possible entries for duplication.
  • It may contain null values for some employees. (correct)
  • It is not unique for each employee.
  • It does not have sufficient data types.

    • Which model is described as the actual design or blueprint of the database?

    <p>Physical ERD</p> Signup and view all the answers

    What is the main purpose of a logical ERD in database modeling?

    <p>To define additional operational and transactional entities.</p> Signup and view all the answers

    What is the primary characteristic of a weak entity?

    <p>It must be defined by a foreign key relationship with another entity.</p> Signup and view all the answers

    Which of the following is true about a derived attribute?

    <p>It is based on another attribute's value.</p> Signup and view all the answers

    Which type of attribute must always have a value?

    <p>Mandatory attribute</p> Signup and view all the answers

    What is a composite attribute?

    <p>An attribute that can be subdivided into meaningful sub-parts.</p> Signup and view all the answers

    What distinguishes a candidate key from other attributes?

    <p>It uniquely identifies a record in a relation.</p> Signup and view all the answers

    Which of the following is NOT an example of a multivalued attribute?

    <p>Employee social security number.</p> Signup and view all the answers

    What role does a unique identifier serve in an entity?

    <p>It distinguishes one entity from another.</p> Signup and view all the answers

    Which type of attribute can be left empty or null?

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

    What is the primary goal of conceptual design in database development?

    <p>To sketch out entities and their relationships</p> Signup and view all the answers

    What is the main outcome of the logical design phase in database design?

    <p>Relation schemas based on ER or Class Diagrams</p> Signup and view all the answers

    Which statement accurately describes normalization in database design?

    <p>It primarily adds tables to eliminate superfluities.</p> Signup and view all the answers

    What is the primary role of an Entity Relationship Diagram (ERD)?

    <p>To illustrate relationships between entities and their attributes</p> Signup and view all the answers

    During which phase of database design is a DBMS selected for implementation?

    <p>Physical Design</p> Signup and view all the answers

    Which component in an ER diagram represents objects or concepts about which information is stored?

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

    What are the key components of an ER diagram?

    <p>Entities, relationships, and attributes</p> Signup and view all the answers

    What purpose does documenting an existing database structure serve?

    <p>Debugging and analyzing its functionality</p> Signup and view all the answers

    What is the minimum requirement for a primary key in a relation?

    <p>It must consist of at least one attribute.</p> Signup and view all the answers

    Which of the following correctly defines a composite key?

    <p>A key composed of multiple attributes.</p> Signup and view all the answers

    What does cardinality specify in relationships between entities?

    <p>The numerical relationship between entities.</p> Signup and view all the answers

    Which type of relationship allows entities to link to themselves?

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

    Which of the following is NOT a component of entity integrity?

    <p>Primary key values can contain null values.</p> Signup and view all the answers

    What is the role of domain integrity in a relational model?

    <p>It restricts the values of attributes in the relation.</p> Signup and view all the answers

    What distinguishes a ternary relationship from other types of relationships?

    <p>It connects three entities directly together.</p> Signup and view all the answers

    Which statement best describes a foreign key?

    <p>It is an attribute from one relation that exists in another relation.</p> Signup and view all the answers

    Study Notes

    Database Concepts - Lecture 3

    • Lecture presented by Dr. Amira M. Gaber
    • Database design phases are crucial for successful applications

    Database Design Phases

    • Conceptual design:

      • Important phase for successful database applications
      • Sketches out entities to be represented
      • Determines the relationship types between entities
      • Defines the scope of the database and general rules

    • Logical design:

      • Also called data modeling/mapping phase
      • Creates relation schemas based on ER or Class Diagrams
      • Relation schemas are generated through a mechanical process
      • Follows rules for transferring ER or class diagram to relation schemas

    • Normalization:

      • Final step in logical design
      • Aims to remove redundancy and anomalies during database updates
      • Changes the relation schema to reduce redundancy
      • Adds new tables with each normalization phase

    • Physical design:

      • Final phase of database design
      • Implements the database design
      • Requires a DBMS (Database Management System) selection

    ERD (Entity Relationship Diagram)

    • ERD is a diagram for visualizing relationships between entities in a database

    • Symbols:

      • Entities are represented by rectangles
      • Attributes are represented by ovals
      • Relationships are represented by diamonds

    • Types of Entities:

      • Weak entity - defined by a foreign key relationship with another entity

    • Types of Attributes:

      • Key attribute - unique characteristic of an entity
      • Multi-valued attribute - can have multiple values
      • Derived attribute - calculated from another attribute
      • Composite attribute - subdivided into meaningful parts

    • Types of Relationships:

      • Relationships represented by lines connecting entities
      • Recursive relationship - entities can be self-linked
      • Binary relationship - two entities are connected directly
      • Ternary relationship - three entities are connected directly

    • Common ERD Symbols:

      • Lines connect entities and relationships
      • Relation names should be verbs
      • Cardinality specifies relationships' numerical attributes (one-to-one, many-to-one, many-to-many)

    Constraints

    • Constraints limit attribute values and relationships allowed in a database
    • Types of Constraints:
      • Domain integrity - restricts attribute values based on real-world semantics
      • Entity integrity - primary key values cannot be null
      • Referential integrity - foreign key must match primary key or be null

    ERD Models

    • Conceptual ERD: Most abstract, higher-level view for business analysts
    • Logical ERD: More detailed, defines operational and transactional entities
    • Physical ERD: Actual design blueprint with technical details (cardinality, foreign/primary keys)

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    Database Concepts Lecture 3 PDF

    Description

    Explore the essential phases of database design in this lecture presented by Dr. Amira M. Gaber. Learn about conceptual design, logical design, normalization, and physical design, and understand how these phases contribute to the development of successful database applications.

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