Understanding Views

A view is a logical table that is based on one or more tables. The view itself contains no data. It is sometimes called a non-materialized view to distinguish it from a materialized view, which does contain data that has already been calculated from detail tables.

Views cannot be updated directly, but changes to the data in the detail tables are immediately reflected in the view.

A view is basically a SQL statement that is stored in a database which enables you to treat the results of a SQL query as a table itself. TimesTen generates the results of a view every time you query that view, so a view always has the latest data results. You can query a view just like you would query a regular table.

A materialized view enables you to precompute expensive SQL operations. There are cases where primarily read-only databases can increase the speed of their SELECT operations by precomputing the results of queries and storing them in a materialized view. The downside in this case is that the materialized view requires additional storage space. Keep in mind that when you perform DML operations on the detail tables of a materialized view, these DML operations are more resource intensive and more storage is required to store the materialized view rows. If you use too many materialized views on a table, this may reduce the performance of that table.

To perform any operation that creates, drops or manages a view, the user must have the appropriate privileges, which are described along with the syntax for all SQL statements in the SQL Statements chapter in the Oracle TimesTen In-Memory Database SQL Reference.

This section includes the following topics:

• Creating a View

• Dropping a View

• Restrictions on Views and Detail Tables