What are views?Why they are used?

Haveing views is a much good thing making it useable to join tbales together but makeings it appear as one tables.
If useing LINQ its is much possible to update tables with veiws as well as haveing.

Many day

Shusta

Hi Amulya,


A view is a virtual table. A view consists of rows and columns just like a table. The difference between a view and a table is that views are definitions built on top of other tables (or views), and do not hold data themselves. If data is changing in the underlying table, the same change is reflected in the view. A view can be built on top of a single table or multiple tables. It can also be built on top of another view


The syntax for creating a view

CREATE VIEW "VIEW_NAME" AS "SQL Statement"

"SQL Statement" can be any of the SQL statements we have discussed in this tutorial.

Let's use a simple example to illustrate. Say we have the following table:

TABLE Customer
(First_Name char(50),
Last_Name char(50),
Address char(50),
City char(50),
Country char(25),
Birth_Date date)

and we want to create a view called V_Customer that contains only the First_Name, Last_Name, and Country columns from this table, we would type in,

CREATE VIEW V_Customer
AS SELECT First_Name, Last_Name, Country
FROM Customer

Now we have a view called V_Customer with the following structure:

View V_Customer
(First_Name char(50),
Last_Name char(50),
Country char(25))

We can also use a view to apply joins to two tables. In this case, users only see one view rather than two tables, and the SQL statement users need to issue becomes much simpler. Let's say we have the following two tables:

Table Store_Information
store_name     Sales     Date
Los Angeles     $1500     Jan-05-1999
San Diego     $250     Jan-07-1999
Los Angeles     $300     Jan-08-1999
Boston             $700     Jan-08-1999

Table Geography
region_name     store_name
East     Boston
East     New York
West     Los Angeles
West     San Diego

and we want to build a view that has sales by region information. We would issue the following SQL statement:

CREATE VIEW V_REGION_SALES
AS SELECT A1.region_name REGION, SUM(A2.Sales) SALES
FROM Geography A1, Store_Information A2
WHERE A1.store_name = A2.store_name
GROUP BY A1.region_name

This gives us a view, V_REGION_SALES, that has been defined to store sales by region records. If we want to find out the content of this view, we type in,

SELECT * FROM V_REGION_SALES

Result:
REGION     SALES
East     $700
West     $2050




Please refer the below link

http://www.1keydata.com/sql/sql-view.html



Thanks