Constructs preventing views from being merged
Some constructs may prevent a view from being (simple-) merged.
If the view contains constructs not inclued in
select-project-views, such as
-
group by / aggregation functions
-
distinct
- Outer join
-
model
-
connect by
- Set operators
If the view is placed on the right side of a semijoin or an antijoin.
If the view has subqueries in the select list.
If the outer query block contains PL/SQL functions.
The view participates in an outer join, and does not meet one of the several additional validity requirements that determine whether the view can be merged.