Sql server ___________session_16(views)

 A view is an "VirtualTable".
 It can have multiple columns and rows from the
one or more table.
 Normally view cannot store the data
permanently in the table.
 Views display only those data which are
mentioned in the query.
 A view consists of a SELECT statement

 Views are used as Security Mechanism of Database.
 A view can be useful when there are multiple users with different levels
of access, who all need to see portions of the data in the database.
 Views can do the following:
 Restrict access to specific rows in a table
 Restrict access to specific columns in a table
 Join columns from multiple tables and present them as though they
are part of a single table
 Present aggregate information (such as the results of the COUNT
function).

General syntax for creating a view:
CREATEVIEW [View_Name]
AS
[SELECT Statement]
As for example :
CREATEVIEW SampleView
As
SELECT EmpID, EmpName FROM
EmpInfo

 This is as similar as select statement of a
table.
SELECT * FROM SampleView

 General syntax:
DROPVIEW viewname;
 Example:
DROPVIEW SampleView;

 When a view is dropped, it has no effect on the underlying
tables.
 Dropping a view removes its definition and all the
permissions assigned to it.

 However, dropping a table that references a view does not
drop the view automatically.
 You must drop it explicitly.

 General syntax:
ALTERVIEW viewname
AS
SELECT…;
 Example:
ALTERVIEW SampleView
AS
SELECT * FROM EmpInfo;

The value for the column is provided
automatically if:
 The column has an IDENTITY property.
 The column has a default value specified.
 The column has a timestamp data type.
 The column takes null values.
 The column is a computed column.

 The value of a column with an IDENTITY
property cannot be updated.
 Records cannot be updated if the base table
contains aTIMESTAMP column.
 While updating a row, if a constraint or rule is
violated, the statement is terminated, an error is
returned, and no records are updated.
 When there is a self-join with the same view or
base table, the UPDATE statement does not
work.

 There are 3 methods to see the view definition:
 Method 1:
Sp_helptext viewname;
 Method 2:
select definition from sys.sql_modules
where object_id=object_id(‘viewname');
 Method 3:
select object_definition(object_id('vv'));

 The sys.sql_modules is a system view. It is
used to display view definition.
 Object_definition() is built-in function that
returns the view definition.
 Object_id() is a system function that returns
the ID of view.

 There are two types of views in the sql server
2005.
 Normal or Standard view
 Partitioned view

 This view is most frequently used by the
developers.
 When we create the view the schema will be
stored as object in the database.
 When we retrieve the content from this virtual
table, it will execute the schema and the stored
data from the parent table.
 These include focusing on specific data and
simplifying data manipulation.

 CREATEVIEW vw_empinfo
AS
SELECT * FROM EmpInfo;
 SELECT * FROM vw_empinfo;
 INSERT INTO vw_empinfo
VALUES(4,’abcd’,’.NET’,565652);
 DELETE FROM vw_empinfo WHERE EmpID = 1;
Here you can do the DML operations in the view when you
have only one table.

 The partitioned view and its execution is like
normal view.
 It will work across the database and across
the server.
 There are two types of Partitioned views.
 Local PartitionedView
 Global PartitionedView

 The local partitioned view can be created
within same server but different database.
 The view schema definition will be stored in
the executed database.

 USE Database1
CREATETABLE EmployeeList
(
iEmployeeID INT IDENTITY(1,1),
vFirstNameVARCHAR(25) NOT NULL,
vLastNameVARCHAR(25) NOT NULL,
iDeptID INT
)
 USE Database2
CREATETABLE Department
(
iDeptID INT IDENTITY(1,1) PRIMARY KEY,
vDeptNameVARCHAR(50),
)

CREATEVIEW vw_LocalPartion_View
AS
SELECT E.iEmployeeID, D.vDeptName
FROM EmployeeList E
INNER JOIN
Database2.dbo.Department D ON D.iDeptID = E.iDeptID ;

 The global Partitioned view will work across the server.
 The view can be created to join the table across the server.
 The accessing format will be like this.
[Server Name]. Database Name.Table Name
 When we execute the view if it is not linked with the current
server then it will ask us to link the external server.

 The following system stored procedure will be used
to link the server.
sp_addlinkedserver 'Server name'
 The following system catalog table is used to see
the list of linked servers.
SELECT * FROM SYS.SERVERS

 There are two different option for creating a
view.
 Schema Binding Option
 Encryption

 If we Creates a view with the SCHEMABINDING option it will
locks the tables being referred by the view and restrict any
kinds of changes that may change the table schema ( No
Alter Command) .
 While creating schema binding view, we can't mention
"Select * from tablename" with the query.
 We have to mention all the column name for reference

CREATEVIEW DemoSampleView
With SCHEMABINDING
As
SELECT EmpID, EmpName, FROM DBO.EmpInfo;
 While specifying the Database name we have
use Dbo.[DbName] .
 This will prevent any of the underlying tables
from being altered without the view being
dropped.

 This option encrypts the definition.
 This option encrypts the definition of the view.
 Users will not be able to see the definition of
theView after it is created.
 This is the main adavatages of view where we
can make it secure.
 Note: Once view is encrypted, there is no way
to decrypt it again.
CREATEVIEW DemoView
With ENCRYPTION
Select ename,edesig from dbo.EmpInfo

Sql server ___________session_16(views)

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Sql server ___________session_16(views)