Module 7: Implementing Views

Overview

Introducing Views

Defining and Using Views

Using Views to Optimize Performance

Lesson: Introducing Views

What Are Views?

Advantages of Views

What Are Views?

EmployeeViewEmployeeView

Lastname Lastname Firstname Firstname

Davolio Fuller Leverling

Davolio Fuller Leverling

Nancy Andrew Janet

Nancy Andrew Janet

EmployeesEmployees

EmployeeIDEmployeeID LastName LastName FirstnameFirstname TitleTitle

123

123

DavolioFullerLeverling

DavolioFullerLeverling

NancyAndrewJanet

NancyAndrewJanet

~~~~~~~~~

~~~~~~~~~

USE NorthwindGOCREATE VIEW dbo.EmployeeViewAS SELECT LastName, FirstnameFROM Employees

USE NorthwindGOCREATE VIEW dbo.EmployeeViewAS SELECT LastName, FirstnameFROM Employees

User’s View

Advantages of Views

Focus the Data for Users

Mask Database Complexity

Simplify Management of User Permissions

Improve Performance

Organize Data for Export to Other Applications

Lesson: Defining and Using Views

The Process of Creating Views

Example: View of Joined Tables

The Process of Altering and Dropping Views

Broken Ownership Chains

Location of View Information

Encrypted View Definition

Restrictions for Modifying Data Through Views

The Process of Creating Views

Creating a View

Restrictions on View Definitions

Cannot include ORDER BY clause Cannot include INTO keyword

CREATE VIEW dbo.OrderSubtotalsView (OrderID, Subtotal)ASSELECT OD.OrderID, SUM(CONVERT(money,(OD.UnitPrice*Quantity*(1-Discount)/100))*100)FROM [Order Details] ODGROUP BY OD.OrderIDGO

CREATE VIEW dbo.OrderSubtotalsView (OrderID, Subtotal)ASSELECT OD.OrderID, SUM(CONVERT(money,(OD.UnitPrice*Quantity*(1-Discount)/100))*100)FROM [Order Details] ODGROUP BY OD.OrderIDGO

USE NorthwindGOCREATE VIEW dbo.ShipStatusViewASSELECT OrderID,ShippedDate,ContactNameFROM Customers c INNER JOIN Orders o ON c.CustomerID = O.CustomerIDWHERE RequiredDate < ShippedDate

USE NorthwindGOCREATE VIEW dbo.ShipStatusViewASSELECT OrderID,ShippedDate,ContactNameFROM Customers c INNER JOIN Orders o ON c.CustomerID = O.CustomerIDWHERE RequiredDate < ShippedDate

Example: View of Joined Tables

Orders Customers

ShipStatusView

OrderIDOrderID102641027110280

102641027110280

1996-08-211996-08-291996-09-11

1996-08-211996-08-291996-09-11

ShippedDateShippedDate1996-08-231996-08-301996-09-12

1996-08-231996-08-301996-09-12

ContactNameContactNameLaurence LebihanGeorg PippsHorst Kloss

Laurence LebihanGeorg PippsHorst Kloss

BONAPPICCOQUICK

BONAPPICCOQUICK

Laurence LebihanGeorg PippsHorst Kloss

Laurence LebihanGeorg PippsHorst Kloss

CustomerIDCustomerID ContactNameContactName

Bon app'Piccolo und mehrQUICK-Stop

Bon app'Piccolo und mehrQUICK-Stop

CompanyNameCompanyName

1066310827104271045110515

1066310827104271045110515

BONAP BONAP PICCO QUICKQUICK

BONAP BONAP PICCO QUICKQUICK

~~~ ~~~ ~~~ ~~~ ~~~

~~~ ~~~ ~~~ ~~~ ~~~

1997-10-031998-02-061997-03-031997-03-121997-05-23

1997-10-031998-02-061997-03-031997-03-121997-05-23

OrderIDOrderID CustomerIDCustomerID ShippedDateShippedDate

1997-09-241998-01-261997-02-241997-03-051997-05-07

1997-09-241998-01-261997-02-241997-03-051997-05-07

RequiredDateRequiredDate

The Process of Altering and Dropping Views

Altering Views

Retains assigned permissions Causes new SELECT statement and options to replace

existing definition

Dropping Views

USE NorthwindGOALTER VIEW dbo.EmployeeViewAS SELECT LastName, FirstName, ExtensionFROM Employees

USE NorthwindGOALTER VIEW dbo.EmployeeViewAS SELECT LastName, FirstName, ExtensionFROM Employees

DROP VIEW dbo.ShipStatusViewDROP VIEW dbo.ShipStatusView

Dependent Objects with Different Owners

Example:

Maria executes:

Pierre executes:

Broken Ownership Chains

GRANT SELECT ON view2 TO pierreGRANT SELECT ON view2 TO pierre

SELECT * FROM maria.view2SELECT * FROM maria.view2

maria.view2maria.view2

lucia.view1lucia.view1

lucia.table1lucia.table1

Location of View Information

Locating View Definitions

Not available if view was created using WITH ENCRYPTION option

Locating View Dependencies

Lists objects upon which view depends

Lists objects that depend on a view

Encrypted View Definition

Use the WITH ENCRYPTION Option

Do Not Delete Entries in the syscomments Table

CREATE VIEW dbo.[Order Subtotals] WITH ENCRYPTIONASSELECT OrderID, Sum(CONVERT(money,(UnitPrice*Quantity*(1-Discount)/100))*100) AS SubtotalFROM [Order Details]GROUP BY OrderIDGO

CREATE VIEW dbo.[Order Subtotals] WITH ENCRYPTIONASSELECT OrderID, Sum(CONVERT(money,(UnitPrice*Quantity*(1-Discount)/100))*100) AS SubtotalFROM [Order Details]GROUP BY OrderIDGO

Restrictions for Modifying Data Through Views

Views Do Not Maintain a Separate Copy of Data

Modifications are done to the actual base table

Restrictions

Must not include aggregate functions or GROUP BY Cannot affect more than one underlying table Cannot be made to certain columns Are verified if the WITH CHECK OPTION has been

specified

Lesson: Using Views to Optimize Performance

Potential Performance Problems

Indexed Views

Partition Data Using Views

Best Practices

Potential Performance Problems

TotalPurchaseViewTotalPurchaseView

11 ~~ ~~ ~~ ~~

22 ~~ ~~ ~~ ~~

33 ~~ ~~ ~~ ~~

44 ~~ ~~ ~~ ~~

55 ~~ ~~ ~~ ~~

66 ~~ ~~ ~~ ~~

CustomersCustomers11 ~~ ~~ ~~ nn

22 ~~ ~~ ~~ nn

33 ~~ ~~ ~~ yy

44 ~~ ~~ ~~ yy

55 ~~ ~~ ~~ nn

66 ~~ ~~ ~~ yy

OrdersOrders11 ~~ ~~ ~~ nn

22 ~~ ~~ ~~ nn

33 ~~ ~~ ~~ yy

44 ~~ ~~ ~~ yy

55 ~~ ~~ ~~ nn

66 ~~ ~~ ~~ yy

Order DetailsOrder Details11 ~~ ~~ ~~ ~~

22 ~~ ~~ ~~ ~~

33 ~~ ~~ ~~ ~~

44 ~~ ~~ ~~ ~~

55 ~~ ~~ ~~ ~~

66 ~~ ~~ ~~ ~~ TopSalesViewTopSalesView

~~ ~~ ~~

~~ ~~ ~~

~~ ~~ ~~

USE NorthwindGOCREATE VIEW dbo.TopSalesViewAS SELECT * FROM dbo.TotalPurchaseView WHERE Subtotal > 50000GO

USE NorthwindGOCREATE VIEW dbo.TopSalesViewAS SELECT * FROM dbo.TotalPurchaseView WHERE Subtotal > 50000GO

SELECT *FROM dbo.TopSalesWHERE CompanyName = 'Ernst Handel'

SELECT *FROM dbo.TopSalesWHERE CompanyName = 'Ernst Handel'

Indexed Views

Indexed Views Store the Result Sets in the Database

Creating an Indexed View

Guidelines for Creating Indexed Views

Use when:

Performance gains outweigh maintenance costs

Underlying data is infrequently updated

Queries perform many joins and aggregations

Restrictions on Creating Indexed Views

Partition Data Using Views

You Can Use Views to Partition Data Across Multiple Servers or Instances of SQL Server

How SQL Server Uses Views to Partition Data

How Partitioned Views Improve Performance

Best Practices

Use a Standard Naming ConventionUse a Standard Naming Convention

dbo Should Own All Viewsdbo Should Own All Views

Verify Object Dependencies Before You Drop ObjectsVerify Object Dependencies Before You Drop Objects

Never Delete Entries In The syscomments TableNever Delete Entries In The syscomments Table

Carefully Evaluate Creating Views Based On ViewsCarefully Evaluate Creating Views Based On Views

Lab A: Implementing Views

Exercise 1: Creating and Testing Views

Exercise 2: Encrypting a View Definition

Exercise 3: Modifying Data Through Views

Exercise 4: Locating View Definitions