Thanks for your explantion. It is very Articulate. I have a question here. What do you mean by locally aggregated in your explanation ? It still be the perm space. is nt it ?
Locally Aggregated : Basically without data movement or inside the amp.You need collect all data in spool file then eliminitate duplicates.
Dieter -Thanks for the update on TD13 ,wasn't aware of that.
@barcoo - Have you compared the EXPLAIN plans of the UNION in a CREATE TABLE AS vs CREATE TABLE and INSERT INTO? Have you tested it yet?