Views
On the surface, a view is nothing more than a SELECT query that is saved with a name in a database.
Code Reuse Saves common queries into objects.
Pros: Code Reuse
The ability to hide all of the query logic, exposing a simple object/table.
CREATE VIEW vProductCosts
AS
SELECT ProductID, Name, StandardCost
FROM Production.Product
To select all from the View
SELECT * FROM vProductCosts
Alter view
ALTER VIEW vProductCosts
AS
SELECT ProductID, ProductSubcategoryID, Name, ProductNumber, StandardCost
FROM Production.Product
Summary
Hiding Complexity
One of the most common, and arguably one of the most important, reasons to use views is to simplify data access. In a normalized database, even the most basic queries can involve many different tables.
View can update data, but should not.