3. Lesson 1: Introduction to Views
• What is a View?
• Types of Views
• Advantages of Views
• Working with System Views
• Dynamic Management Views
• Demonstration 1A: System and Dynamic Management
Views
4. What is a View?
• A view is a database object referenced like a table
• A view is like a SELECT query with a name
Employee (table)
EmployeeID LastName FirstName Title BirthDate …
287 Mensa-Annan Tete Mr. 3/2/1984 …
288 Abbas Syed Mr. 4/5/1976 …
289 Valdez Rachel NULL 9/8/1973 …
EmployeeList (view)
EmployeeID LastName FirstName
287 Mensa-Annan Tete
288 Abbas Syed
289 Valdez Rachel
5. Types of Views
• Standard views
Combine data from one or more base tables into a new virtual
table
• System Views
Provide state information for SQL Server and catalogs
• Indexed views
View that has been computed and stored. You index a view by
creating a unique clustered index on it
• Partitioned views
Joins horizontally partitioned data from a set of tables across one
or more servers
6. Advantages of Views
• Focus the data for a user
• Mask database complexity
• Simplify management of user permissions
• Organize data for export to other applications
• Provide backward compatibility
• Structure data for reporting applications
7. Working with System Views
There are several types of system views:
• Catalog Views
Return information used by the SQL Server Database Engine
• Compatibility Views
Many system tables available in earlier versions are now available
as system views
• Information Schema Views
Provide catalog information as defined in the ISO standard for the
INFORMATION_SCHEMA.
8. Dynamic Management Views
• Return server state information
• Named like sys.dm_*
• Some are implemented as functions, some as views
• Monitor server health
• Diagnose problems, tune performance
9. Demonstration 1A: System and Dynamic
Management Views
In this demonstration, you will see how to:
• Query system views
• Query dynamic management views
10. Lesson 2: Creating and Managing Views
• Creating Views
• Dropping Views
• Altering Views
• Ownership Chains and Views
• Sources of Information about Views
• Updatable Views
• Obfuscating Views Definitions
• Demonstration 2A: Implementing Views
11. Creating Views
• Use the CREATE VIEW Transact-SQL statement:
CREATE VIEW HumanResources.EmployeeList
AS
SELECT EmployeeID, LastName, FirstName
FROM HumanResources.Employee;
• Restrictions on creating views:
Cannot nest more than 32 levels deep
Cannot use ORDER BY without TOP
12. Dropping Views
• Drop by using the DROP VIEW Transact-SQL statement:
DROP VIEW HumanResources.EmployeeList;
• Also drops all permissions associated with the view
• Multiple views can be dropped in a single statement
Comma-delimited list of views
13. Altering Views
• Alter by using the ALTER VIEW Transact-SQL statement:
ALTER VIEW HumanResources.EmployeeList
AS
SELECT EmployeeID, LastName, FirstName, PostalCode
FROM HumanResources.Employee;
• Replaces the definition of a view
• Does not alter permissions associated with the view
15. Sources of Information About Views
SQL Server Management Studio
Source Information
List of views in database
Object Explorer Access to columns, triggers, indexes,
and statistics defined on views
View Properties dialog box Properties of individual views
Transact-SQL
Source Information
sys.views List of views in database
Function that returns definition of non-
OBJECT_DEFINITION()
encrypted views
Objects (including views) that depend
sys.sql_expression_dependencies
on other objects
16. Updatable Views
• Views do not maintain a separate copy of data
• Updates to views modify the base tables
• Updates are restricted by using the WITH CHECK OPTION
• Restrictions:
• Cannot affect more than one base table
• Cannot modify columns derived from functions or expressions
• Cannot modify columns affected by GROUP BY, HAVING, or
DISTINCT clauses
17. Obfuscating View Definitions
• WITH ENCRYPTION clause
• Encrypts view definition stored in SQL Server
• Protects view creation logic to a limited extent
• Generally not recommended
CREATE VIEW HumanResources.EmployeeList
WITH ENCRYPTION
AS
SELECT EmployeeID, LastName, FirstName
FROM HumanResources.Employee;
Use WITH ENCRYPTION on ALTER VIEW to retain encryption
18. Demonstration 2A: Implementing Views
In this demonstration, you will see how to:
• Create a view
• Query a view
• Query the definition of a view
• Use the WITH ENCRYPTION option
• Drop a view
• Generate a script for an existing view
19. Lesson 3: Performance Considerations for Views
• Views and Dynamic Resolution
• Nested View Considerations
• Partitioned Views
• Demonstration 3A: Views and Performance
20. Views and Dynamic Resolution
• Dynamic resolution in view optimization can assist
performance
• SQL Server does not retrieve data that it doesn’t need
• Single query plan for both query and view
• Query plans do not show standard views
• SELECT * needs special consideration in views
Should be avoided
21. Nested View Considerations
• Views can provide a convenient layer of abstraction in
coding
• Views can be nested up to 32 levels
• Nested views can hide code complexity
More difficult to troubleshoot performance issues
More difficult to understand code complexity
22. Partitioned Views
Joins partitioned data from set of tables across servers
SQLServerNorth.Sales.Sale SQLServerSouth.Sales.Sale
CREATE VIEW Sales.AllSales AS
SELECT * FROM
SQLServerNorth.Sales.Sale
vSales
UNION ALL
SELECT *
FROM SQLServerSouth.Sales.Sale;
23. Demonstration 3A: Views and Performance
In this demonstration, you will see how:
• Views are eliminated in query plans
• Views are expanded and integrated into the outer query
before being optimized
24. Lab 4: Designing and Implementing Views
• Exercise 1: Design, Implement and Test the WebStock
Views
• Exercise 2: Design and Implement the Contacts View
• Challenge Exercise 3: Modify the AvailableModels View
(only if time permits)
Logon information
Virtual machine 623XB-MIA-SQL
User name AdventureWorksAdministrator
Password Pa$$w0rd
Estimated time: 45 minutes
25. Lab Scenario
A new web-based stock promotion system is being rolled
out. Your manager is very concerned about providing access
from the web-based system directly to the tables in your
database. She has requested you to design some views that
the web-based system could connect to instead.
Details of organizational contacts are held in a number of
tables. The relationship management system being used by
the account management team needs to be able to gain
access to these contacts. However, they need a single view
that comprises all contacts. You need to design, implement
and test the required view.
Finally, if you have time, a request has been received from
the new Marketing team that the catalog description of the
product models should be added to the AvailableModels
view. They would appreciate you modifying the view to
provide this additional column.
26. Lab Review
• What considerations are there for views that involve
multiple tables?
• What is required for columns in views that are created
from expressions?
