Re: Ref: Performance

> > Cheryl, > > I tried to e-mail this reply to you, but the mail bounced. Maybe the > information would be useful to others, anyway..... > Thank you Joe for this informative post, I'm glad it floated across here. It comes at a timely time. It's also clear enough that even I can understand it. However, I feel that you missed something. Adding columns to an index is fine and good if you will be querying with values for the fields from that index. But adding column XYZ to an index does not mean that a query against the table in question will start using XYZ by itself. (feel free to correct me anyone) but unless you are using the first part of the composite index in the read - any additional part will not be used in the query. I do not know if an index such as: idx_1 (col_1, col_2, col_3, col_4) will be used when querying with values for col_1 and col_4. It WILL be used at a minimum (unless there is another index on col_1) for col_1, but I am unsure whether the query will benefit from col_4 in the index. j. _____________________________________________________________________________ Jack Parker | Hewlett Packard, BSMC Boise, Idaho, USA| Someday you'll go far, jparker@hpbs3645.boi.hp.com | if you catch the right train. (208) 396-5388 (W) (208) 384-1623 (H) | _____________________________________________________________________________ Any opinions expressed herein are my own and not those of my employers. _____________________________________________________________________________