This is an old answer (maybe not valid anymore with so many oracle
releases having come and gone but), the answer is: it doesn't make any
noticable difference from a performance aspect. The bigger question
is: which index will be used more often. I was at an oracle
conference many many years ago, somebody studied this exact question.
He demonstrated empirically that there was no difference to be
measured. Both indexes performed equally well under all his test
scenarios. If your us of the index is both columns all the time then
the order is generally not important. If however, you may be taking
advantage of leading portion scans of the index then pick the column
that you can use most ofter (assuming it gets used at all).
Received on Thu Aug 02 2001 - 12:15:51 CDT
