View Updating rule

What makes oracle not to achieve View Updating rule?

The veiw should contain all the not null columns from the combination of base tables used for creating that particular view....
Then only it is updateble...

please find a related discussion [URL="http://download-uk.oracle.com/docs/cd/B28359_01/server.111/b28310/views001.htm#i1006232"]here[/URL].

Rule description general rule any insert, update, or delete operation on a join view can modify only one underlying base table at a time. Update rule all updatable columns of a join view must map to columns of a key-preserved table. If the view is defined with the with check option clause, then all join columns and all columns of repeated tables are not updatable. Delete rule rows from a join view can be deleted as long as there is exactly one key-preserved table in the join. If the view is defined with the with check option clause and the key preserved table is repeated, then the rows cannot be deleted from the view. Insert rule an insert statement must not explicitly or implicitly refer to the columns of a non-key-preserved table. If the join view is defined with the with check option clause, insert statements are not permitted.

The View should not contain distinct keyword,rownum keyword,group by clause to perform dml operations through it.

[QUOTE=subravin;35894]The View should not contain distinct keyword,rownum keyword,group by clause to perform dml operations through it.[/QUOTE]

Rownum is not a keyword. It is a pseudo column.