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