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Similar performance benefits can be gained with SQL Server by basing your reports on views. A simple solution to the issue of implementing row-level and column-level security is to revoke all permissions to the underlying tables.

For example, the following view selects a customer's total orders and contains joins between the Customers table, the Orders table, and the Order Details table. Instead, define views with only selected columns to implement column-level security and define views with a clause to implement row-level security.

The SQL UPDATE VIEW command can be used to modify the data of a view.

An updatable view is one which allows performing a UPDATE command on itself without affecting any other table. The view is defined based on one and only one table. The view must include the PRIMARY KEY of the table based upon which the view has been created. The view should not have any field made out of aggregate functions. The view must not have any DISTINCT clause in its definition. The view must not have any GROUP BY or HAVING clause in its definition. The view must not have any SUBQUERIES in its definitions. If the view you want to update is based upon another view, the later should be updatable. Any of the selected output fields (of the view) must not use constants, strings or value expressions.

Unlike stored procedures (which also support parameters), these parameterized functions can be updateable, as you'll see later in this chapter.

The SQL-92 standard also mandates that views cannot be sorted with an values with a view; to support that, it also supports sorting.

Views can be used in place of tables in your Access front-end application, whether you're using an Access database or an Access project.

They can be used to provide row- or column-level access to data, to wrap up complex joins, to perform complex aggregate queries, and to otherwise customize the display of data. In this chapter, learn how to define, create, and modify views, and how to perform index analysis and optimize performance in SQL Server. The biggest problem is that just when you get used to accepting a limitation, Microsoft comes up with an amazing, new feature that overcomes it!

The following Transact-SQL statement selects all the data for the view shown in Listing 9.1, sorting the result set on the Company Name column: statement wouldn't have to change. Company Name Views are created inside individual databases, however, views can reference tables and views in other databases or even on other servers (if the view is defined using distributed queries).

The information about where the data in a view comes from and how it is pulled together from various tables is all encapsulated inside the view. Here are some general guidelines for creating views: Views are frequently used as security mechanisms to prevent users from having direct access to tables while still allowing them to work with data.

This can be implemented using the Once the view is created, its definition will be unreadable, as shown in Figure 9.2.

Therefore, make sure that you save your view definition in a script file in case you ever need to modify it.

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