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Interview Questions and Answers on SQL Server View


    What is a View?

       Views are virtual tables that hold data from one or more tables. It is a query stored in the database as object. A view does not contain any data itself, it is a set of queries that are applied to one or more tables that are stored within the database as an object 

What is the use of view?

  1. It allows you to reuse code without  having to write the same complex SQL code over and over.
  2. Views are used for security purposes in databases. Views restrict the user from viewing certain columns and rows. In other words, using a view we can apply the restriction on accessing specific rows and columns for a specific user 

Can we use ORDER BY clause inside a view? 
The ORDER BY clause is invalid in views, inline functions, derived tables, subqueries, and common table expressions, unless TOP or FOR XML is specified.

 Can we update a view?
     If the view contains joins between multiple tables, you can only insert and update one table in the view, and you can't delete rows.  

You can't modify data in views that use GROUP BY or DISTINCT statements. 

 All columns being modified are subject to the same restrictions as if the statements were being executed directly against the base table.
      
The WITH CHECK OPTION clause forces all data-modification statements executed against the view to adhere to the criteria set within the WHERE clause of the SELECT statement defining the view. Rows cannot be modified in a way that causes them to vanish from the view.
    

 Can anyone update a table which is used in a view? How you can prevent that?

     Schema binding binds your views to the dependent physical columns of the accessed tables specified in the contents of the view, i.e. if a view say vw_CustomerBill is schema bind no one will be able to alter the base table dbo.Customer table unless they drop the table.

 Note: Why would we need Schemabinding?

It prevents your views from being orphaned. Just think that someone drops/alters the table dbo.Customer without paying any heed to our view. Now that would leave our view nowhere. Hence schema bind it, this will prevent any such accidents from happening.Also to be able to create an index on the view you need it essentially schema bound.

ALTER VIEW vw_billing
WITH SCHEMABINDING
AS
SELECT C.FName
,C.LNme
,P.ProductDesc
,B.DateOfBooking
,P.Price
,B.QTY
,(B.QTY*P.Price) AS TotalAmountPayable
FROM dbo.BookMaterials B
INNER JOIN dbo.PRODUCT P
ON B.ProductID=P.ProductID
INNER JOIN dbo.Customer C
ON B.CustID=C.CustID;


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