Views are virtual tables formed by a query. A view is a dictionary object that you can use until you drop it.
Views are not updatable.
If a qualified view name is specified, the schema name cannot begin with SYS.
A view definition can contain an optional view column list to explicitly name the columns in the view. If there is no column list, the view inherits the column names from the underlying query. All columns in a view must be uniquely named.
View definitions are
dependent on the tables and views referenced within the view definition. DML
(data manipulation language) statements that contain view references depend
on those views, as well as the objects in the view definitions that the views
are dependent on. Statements that reference the view depend on indexes the
view uses; which index a view uses can change from statement to statement
based on how the query is optimized. For example, given:
the
following SELECT:
is dependent on view V1, table T1, and external scalar function SIN.