Re: Query rewrite

From: Paul <paul_at_see.my.sig.com>
Date: Sun, 17 Jul 2005 14:19:30 +0100
Message-ID: <bbmkd19up598q9onbktlfujkiscse2s5mu@4ax.com>

"Ryan S" <rshevchi_at_vt.edu> wrote:

>There aren't too many updates throughout the day but the customer
>always wants to see the most recent information. What would a
>materialized view buy me here, i'm not that familiar with them?

Please don't top-post.

A materialised view is, well, er... a view that is materialised.

That means that instead of being a virtual table, the view is an actual table which takes up space on the disk and is not just formed on the fly as is the case with normal views.

If you're updating infrequently and your view is complex, materialised views can sometimes provide performance benefits.

From the concepts guide

A materialized view provides indirect access to table data by storing the results of a query in a separate schema object. Unlike an ordinary view, which does not take up any storage space or contain any data, a materialized view contains the rows resulting from a query against one or more base tables or views. A materialized viewcan be stored in the same database as its base tables or in a different database.

Materialized views stored in the same database as their base tables can improve query performance through query rewrites. Query rewrites are particularly useful in a data warehouse environment.

Paul...

-- 

plinehan __at__ yahoo __dot__ __com__

XP Pro, SP 2, 

Oracle, 9.2.0.1.0 (Enterprise Ed.)
Interbase 6.0.1.0;

When asking database related questions, please give other posters 
some clues, like operating system, version of db being used and DDL.
The exact text and/or number of error messages is useful (!= "it didn't work!").
Thanks.
 
Furthermore, as a courtesy to those who spend 
time analysing and attempting to help, please 
do not top post.

Received on Sun Jul 17 2005 - 08:19:30 CDT