Views in a SQL are virtual tables that are compiled at run time. The data that we look in views are not physically stored in the views , but it is stored on main Table. We can make a view on one or more database tables. Normally we take those columns in view that we need to query more time. Once you have created the view, you can query view like as table.
In SQL Server we make views for security reason since it restricts the user to view some columns/ of the table. Views are show only those columns that are present in the query which is used to making time of View .View also provide Abstraction advantage, by which End user not see all table column that are store in database Table.
Syntax for View
CREATE VIEW [view_name]
AS
[select_statement]
Types Of Views
In SQL we have two Types of Views..
1. System Defined Views and
2. User Defined Views.
System Defined Views
System defined Views are that types of Views that already exist in the Master
database of SQL Server. That Views (System Defined) will be automatically
joined to any user defined database.
User Defined Views
When User make any view by self then that type of View are called User Defined
Views .
There are two types of user defined views.
1. Simple View
2. Complex View
Simple View
When any user made a View by using Single table columns then that Views are called Simple view. In a simple view we can delete, update and Insert data. Insert operation are perform on simple view only if we have primary key and all not null fields in the view.
Example:
It produced following result
Now, I make a View..
It produced following result
In this View we can also Insert, Update and Delete data and that changes are applied on base table.
And again if you want to show User table data then it show updated record, Like this
Complex View
When any user made a View by using more than one tables then that Views are called Complex view.
We can only update data in complex view. you can't insert data in complex view.
We can Update data in Complex View, But we cannot Insert data in Complex view
Now I insert data on vw_User_Personal_Info View then it give the following result..
In this article I try to explain the view in sql server with example. I hope after reading this article your sql views concepts will be strong.
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