A view is a table which provides a user with a defined view of other tables in the database. In contrast to a base table, a view is not stored permanently in the database. The contents of a view are derived when needed. The data in a view only exists in the underlying base tables.
Thus a view always contains the values which are contained in the database at the point in time when the view is evaluated.
Views provide a number of advantages: flexibility when querying the database, reduced storage space requirements and the option of a graded data protection mechanism:
Correctly defined views allow data to be grouped in such a way that it exactly meets the information requirements of each user.
It is not necessary to create new storage space each time different combinations of data are required.
It is possible to grant nonprivileged users access to the data in the database only via appropriate views on selected data (see "Access protection in connection with views").
The CREATE VIEW statement creates a view; the DROP VIEW statement deletes a view. If the view is queried using this name, it represents a base table as far as the user is concerned.
Updatable views can be used to insert, modify and delete rows in the underlying base tables. A view is updatable if a query expression is specified in the CREATE VIEW statement and the underlying query expression is updatable (see "Query expression").