SQL Server views - August 29, 2008 at 18:00 PM by Nishant Kumar
Define Views.
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View can be created to retrieve data from one or more tables.
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Query used to create view can include other views of the database.
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We can also access remote data using distributed query in a view.
Views - October 24, 2008 at 18:10 pm by Rajmeet Ghai
What is Indexed view? How to create it?
In an indexed view, the data is already computed and stored. Data can be
accessed by a unique index. This index is a clustered index. In order to create
an index the syntax is
CREATE [UNIQUE], [CLUSTERED | NONCLUSTERED] INDEX index_name
ON {view}
[WITH <index_option>]
[ON filegrp]
What are partitioned views and distributed partitioned views?
Partitioned views allow data in a large table to be split into smaller tables.
These small tables are called as member tables. The split is done based on
range of data values in one of the columns.
In a distributed portioned view, each member table is on a separate member
server. This means that the member tables are distributed. To locate these
tables easily, the database name on each server should be same.
What functions can a view be used to performed?
Functions of View:-
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Subset data of a table
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Can join multiple tables values into one
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They can act as aggregated tables. i.e. a view can be used to store Sum,
average of values
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Views can be nested and can be used for abstraction
Define views.
Answer
A view can be considered as a virtual table. It does not physically
exist. It is based on the result set of a SQL statement. A view contains rows
and tables just like a real table.
Describe the functionalities that views support.
Answer
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Views can subset data in a table
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They can join multiple tables into one virtual table
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Views can provide security and decrease complexity
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They save space because only their definition is stored.
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They can also be used to create abstraction
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Materialized views are commonly used in data warehousing. They represent a
snapshot of the data from remote sources.
Views can create other calculated fields based on values in the real underlying
tables
Explain Indexed views and partitioned view with their syntax.
Answer
Indexed view:
An index view has a unique clustered index created on it. They exist as rows on
the disk. Because they are saved on the disk, the response time to a query is
fast at the cost of space consumption. They are more commonly used in scenarios
when data modification is less.
Syntax:
Create Index CREATE [UNIQUE ] [ CLUSTERED | NONCLUSTERED ] INDEX index_name ON
table_name
The view is created using the CREATE VIEW synatx
Partitioned view:
Partitioned view joins the horizontally portioned data. This data may belong to
one ore more servers. It makes the data appear as one table. A portioned view
can either be local or distributed. A local portioned view resides on the same
instance of the SQL server while the distributed may reside on a different
server.
Syntax:
The view is then created by UNIONing all the tables and an updateable
partitioned View results
Server 1 :
CREATE TABLE Customer1 (CustomerID INTEGER PRIMARY KEY CHECK (CustomerID
BETWEEN 1 AND 32999), ... -- Additional column definitions)
Similar tables created for Server 2 and 3
Partitioned view for server 1
CREATE VIEW Customers AS
SELECT * FROM CompanyDatabase.TableOwner.Customer1
UNION ALL
SELECT * FROM Server2.CompanyDatabase.TableOwner.Customer2
UNION ALL
SELECT * FROM Server3.CompanyDatabase.TableOwner.Customer3
What are the restrictions that views have to follow?
Answer
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Since a view is a virtual table – columns of the view cannot be renamed. To
change anything in the view, the view must be dropped and create again.
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The select statement on the view cannot contain ORDER BY or INTO TEMP
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When a table or view is dropped, any views in the same database are also
dropped.
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It is not possible to create an index on a view
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It is not possible to use DELETE to update a view that is defined as a join.
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