Systems Chapter 4

  1. Objective of logical base design
    to transform the conceptual data model into a set of relations used for physical database design
  2. Three components of a relational data model
    • -Relational data structure: where data is stored
    • -Data Manipulation: operations used to manipulate data in the data structure
    • -Relational Data Integrity: rules that maintain integrity of the data when manipulated
  3. Relation
    the main data structure that stores and organized data in the relational data model

    • - Column = attribute
    • - Row = record/tuple
  4. Properties of a Relation
    -Each relation is uniquely identified by its name

    -Each cell of a relation contains exactly one (atomic) value

    -Each record of a relation is unique

    -Each attribute in a relation has a distinct name

    -The values of an attribute are from the same domain

    -The order of attributes is irrelevant

    -The order of records is also irrelevant
  5. Composite Key
    key with more than one attribute
  6. Super Key
    is a set of one or more attributes that uniquely identifies each record in a relation
  7. Candidate Key
    is a minimal super key (minimum number of attributes)
  8. Primary Key
    a candidate key that has been selected to uniquely identify records in a relation
  9. Primary Key Properties
    • -Must be unique within its domain at all times
    • -The candidate key can never change
    • -It cannot hold a NULL value
  10. Foreign Key
    attribute or set of attributes in a relation that serves as a primary key of the same or some other relation
  11. Three Types of Data Integrity Constraints
    • -Domain Constraints: all values of an attribute must be from the same domain
    • -Entity Constraints: ensure that every relation of a relational data model has a primary key and that it is not null
    • -Referential Constraints: assures consistency between two relations that are linked through the primary key-foregin key relationship
  12. Domain
    set of values that can be assigned to an attribute
  13. Normalization
    refers to a series of tests performed on relations to determine whether they satisfy or voilate the requirements of a normal form
  14. Data Redundancy
    • having duplicate data in the database
    • -Increases storage use
    • -Reduces efficiency of data updates
  15. Anomalies
    inconsistency problems caused by relations with redundant data
  16. Insertion Anomalies
    Abnormalities encountered while inserting new records into the relation
  17. Deletion Anomalies
    occur when data had been unintentionally removed from the relation
  18. Update Anomalies
    occur when there are multiple changes required to reflect a single attribute change
  19. Functional Dependency
    a relationship among attributes with a RELATION
  20. Determinants
    Attributes on the left-hand side of the arrow in a functional dependency representation

    -if all attributes appear in the functional dependency representation then the determinant is the super key
  21. Dependency Diagram
    a pictorial representation of a functional dependency
  22. Partial Dependency
    functional dependency in which a non-primary key's attributes functionally depent of a part of (but not all) the primary key attributes
  23. Transitive Dependency
    functional dependency in which a none of the attributes involves attributes of a primary key
  24. First Normal Form
    each cell in the relation contains exactly one value
  25. Second Normal Form
    • -Already in first normal form
    • -No partial functional dependencies
  26. Third Noral Form
    • -Already in second normal form
    • -No transitive dependencies
  27. Boyce-Codd Normal form
    • -Already in third normal form
    • -Every deteminant is a candidate key
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Systems Chapter 4
Chapter 4