Re: Difference between Snapshots (user_snapshots) and Views (user_views) in Oracle

On Jan 24, 3:27 pm, "Cathy Hui" <kaka...._at_gmail.com> wrote:
> What is the different between Snapshots and View? I am trying to
> understand it's concept and make sure i am understanding it correctly.
>
> Questions of Snapshot:
> Can Snapshot also be created on a view?
> When user update the table, does the snapshot become invalid
> immeidately?
> When a snapshot become invalid, does this snapshot still stay in the
> database?
>
> Questions of View:
> Is a view static or dynamic (i.e. will the user able to view the
> changes made to the table(s) associate with the view)?
> When a view become invalid, does the view still stay in the database?
>
> Beside these questions I asked above, also feel free to add more
> comment / remarks regarding the difference between a snapshot and a
> view.
>
> Thank you!!!!

A snapshot or materialized view, as the feaute is now normally referred to, is a table built and maintained (updated) by the rdbms using a query.

A view on the other hand is just a stored query definition that is not allocated anywhere. At execution time Oracle handles the viiew in one of 3 ways. It merges the view code into the submitted query against the view and executes the resulting query. It merges the query into the view and executes the resulting query or It fires the view and stores the results in a temp segment and then queries against this temp segment.

HTH -- Mark D Powell -- Received on Wed Jan 24 2007 - 19:45:04 CST