Views - PowerPoint PPT Presentation

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Views

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A virtual table that comprises the fields of one or more tables in the database ... Make certain that a view diagram and View Specifications Sheet exists for each view ... – PowerPoint PPT presentation

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Title: Views


1
Views
  • Chapter 12

2
What Are Views?
  • A virtual table that comprises the fields of one
    or more tables in the database
  • It is a virtual table since it does not store or
    contain data
  • Only its structure is saved the data is
    re-created each time it is accessed

3
Value of Views
  • They can be used to work with data from two or
    more tables
  • They reflect the most up-to-date information
  • They can be fitted to the specific needs of an
    individual or group
  • They can be used to help enforce data integrity
  • They can be used for security or confidentiality
    purposes

4
Anatomy of a View
  • Views can be based on a single table, multiple
    tables, other views or a combination of tables
    and values
  • Can use the fields from the structures they
    comprise
  • Structures that compose the view are called base
    tables or base views

5
Data Views
  • Used to examine and manipulate data from base
    tables
  • Certain fields from the base tables are used to
    create the views structure
  • Data in a single-table data view can be modified
    at any time (except when there are rules that
    specify otherwise)

6
Data Views (cont.)
  • Data views based on two or more tables can be
    created as well as long as relationship exist
  • Data redundancy is allowed since it is not a real
    table that stores data
  • A view does not contain a primary key

7
Aggregate Views
  • Purpose is to display information that is the
    result of aggregating a particular set of data in
    a specific manner
  • Includes one or more calculated fields that
    incorporate the functions that aggregate the data
    and one or more data fields to group the
    aggregate data

8
Aggregate Views (cont.)
  • Data cannot be modified in an aggregate view
  • Calculated fields are noneditable
  • Data fields are used for grouping purposes only
  • Best used as the basis of a report or as a means
    of providing various types of statistical
    information

9
Validation Views
  • Similar to validation tables in that they are
    used to implement data integrity
  • Must be explicitly defined since it will store
    data
  • Constructed with fields from base tables and
    draws data from those tables
  • Usually built from a single table and comprise
    only two or three fields

10
Determining and Establishing Views
  • Views can be a substantial asset to the database
  • Views are used as a tool to support particular
    aspects of the implementation or application
    program

11
Working with Users and Management
  • Identify the types of views required by the
    organization
  • Suggestions to identify requirements
  • Review notes with the group
  • Review data-entry report, and presentation
    samples gathered during the early stages of the
    design process
  • Examine the tables and subjects they represent
  • Analyze the table relationships
  • Study the business rules

12
Establishing Views
  • Using calculated fields where appropriate
  • Imposing Criteria to Filter the Data
  • Using a View Specifications Sheet to Record the
    View
  • Name
  • Type
  • Base Tables
  • Calculated Field Expressions
  • Filters

13
Reviewing the Documentation for Each View
  • Make certain that the view is properly
    constructed
  • Make certain that the calculated fields created
    are suitable for the View
  • Make certain that the filters will retrieve the
    required records
  • Make certain that a view diagram and View
    Specifications Sheet exists for each view
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