ما الفائدة من الviews فى الحياة العملية

السلام عليكــم ورحمـة الله وبركاتــه ،،

حضرتك موصلتش لحل ياتري ممكن مين يوصل :S بس اكيد اكيد لها مميزات مش عند حد تانى مثل الفرق بين لغات البرمجه

بس بصراحه افضل شغل لى مع ال Views هى البيانات المتدخله

يعنى احيانا نعمل View مركب ومربوط بى View اخري وهكذا

<h1 class="firstHeading">Views - Advantages and Disadvantages</h1>

Advantages

Views are used for several different reasons

To hide data complexity. Instead of forcing your users to learn the T-SQL JOIN syntax you might wish to provide a view that runs a commonly requested SQL statement.

To protect the data. If you have a table containing sensitive data in certain columns, you might wish to hide those columns from certain groups of users. For instance, customer names, addresses and their social security numbers might all be stored in the same table; however, for lower level employees like shipping clerks, you can create a view that only displays customer name and address. You can grant permissions to a view without allowing users to query the underlying tables.

There are a couple of ways you might want to secure your data

Create a view to allow reading of only certain columns from a table. A common example of this would be the salary column in the employee table. You might not want all personnel to be able to read manager's or each other's salary. This is referred to as partitioning a table vertically and is accomplished by specifying only the appropriate columns in the CREATE VIEW statement.

Create a view to allow reading only certain rows from a table. For instance, you might have a view for department managers. This way, each manager can provide raises only to the employees of his or her department. This is referred to as horizontal partitioning and is accomplished by providing a WHERE clause in the SELECT statement that creates a view.

Enforcing some simple business rules. For example, if you wish to generate a list of customers that need to receive the fall catalog, you can create a view of customers that have previously bought your shirts during the fall.

Data exports with BCP. If you are using BCP to export your SQL Server data into text files, you can format the data through views since BCP's formatting ability is quite limited.

Customizing data. If you wish to display some computed values or column names formatted differently than the base table columns, you can do so by creating views.

Disadvantages

Even though views can be a great tool for securing and customizing data, they can be slow. Indeed, they are not any faster than the query that defines them. With SQL Server 2000, 2005 indexed views (also referred to as "materialized" views) are supported to overcome this limitation.

Views can especially degrade the performance if they are based on other views. Therefore, it is recommended NOT to create views based on other views. All views should be created against base tables.