Supporting views
MySQL 5.0 introduced support for named and updatable views (more details are available at http://dev.mysql.com/doc/refman/5.5/en/views.html). A view is a derived table (consider it a virtual table) whose definition is stored in the database. A SELECT statement done on one or more tables (or even on views), can be stored as a view and can also be queried.
Views can be used to:
Limit the visibility of columns (for example, do not show salary information)
Limit the visibility of rows (for example, do not show data for specific world regions)
Hide a changed table structure (so that legacy applications can continue to work)
Instead of defining cumbersome column-specific privileges on many tables, it's easier to prepare a view containing a limited set of columns from these tables. We can then grant permissions on the view as a whole.
To activate support for views on a server after an upgrade from a pre-5.0 version, the administrator has to execute the mysql_upgrade program, as described...
