18.3. Types of VIEWs
The type of SELECT statements and their purpose can classify VIEWs. The strong advantage of a VIEW is that it will produce the correct results when it is invoked, based on the current data. Trying to do the same sort of things with temporary tables or computed columns within a table can be subject to errors and slower to read from disk.
18.3.1. Single-Table Projection and Restriction
In practice, many VIEWs are projections or restrictions on a single base table. This is a common method for obtaining security control by removing rows or columns that a particular group of users is not allowed to see. These VIEWs are usually implemented as in-line macro expansion, since the optimizer can easily fold their code into the final ...