Re: index on multiple columns vs multiple indexes on single column

cumin wrote:
> Could someone explain (or point out the relevant documentation about)
> situations in which you would want to index several columns vs making
> multiple indexes, one for each column? Also, I understood that the
> order of columns in a multi-column index was important, but I do not
> understand why.
>
> Thank you.

You would want to make the decision about which way to go as follows:

1. Collect all relevant SQL statements used to select from, update, and/or delete from the table.
2. You test them all using EXPLAIN PLAN and/or AUTOTRACE.
3. You test different ways of building the index and choose the one that provides the most efficiency.

There is no magic bullet.

-- 
Daniel A. Morgan
http://www.psoug.org
damorgan_at_x.washington.edu
(replace x with u to respond)