Re: oracle indexes
Date: Fri, 06 Jun 2008 03:01:28 GMT
"joel garry" <joel-garry_at_home.com> wrote in message
On Jun 4, 9:01 pm, doug <douglass_da..._at_earthlink.net> wrote:
> Say If I have a table with column a, and column b (say they are
> Sometimes I will do a query with a where clause that just references
> column a.
> Sometimes I will do a query with a where clause that references both
> column a and b.
> Is there a need to create an index with a, and an index with a, b? Or
> will an index with a,b work for both of the above types of queries?
> I know in mysql if I have an index (a, b, c), then it is useful for
> queries referencing a or a,b or a, b,c. But, I am not as familiar
> with how Oracle indexes work.
You should read about indexing in the concepts manual and the performance tuning manual. You can also search http://tahiti.oracle.com for the skip scan Jim mentioned, which answers your question.
Once you become comfortable with the basic concepts, you can delve deeper in many places, especially http://richardfoote.wordpress.com/ (be sure and check out the index internals presentation).
-- @home.com is bogus. “I just don't understand why kids would do a stupid thing like that...” http://www.signonsandiego.com/uniontrib/20080605/news_1n5nude.html I had forgotten to mention Richard Foote's web site. It is excellent. Lots of fantastic information there. JimReceived on Thu Jun 05 2008 - 22:01:28 CDT