Individual Indexes v.s. One "combinded" Index

From: David Hiltz <dhiltz_at_whsun2.whoi.edu>
Date: Sat, 8 Oct 1994 14:58:05 GMT
Message-ID: <CxD08t.957_at_netnews.whoi.edu>

    I just read in the "Oracle 7 Server - SQL Language Reference Manual",     pg. 4-162 ("Index Columns") that if you have a "combined index" of     column A,B and C on a table and you reference column B; C; or B,C - the     index is not used. You would have to reference from left to right (ie.     A; A,B; or A,B,C).

    I created six individual indexes on a table and the indexes used a total     of 7.5Megs. One index that contained the six columns used 2.3Megs.

    So its a trade off of disk space v.s. use of index. Also, with     individual indexes I can drop any of the six indexes without effecting     the other indexes (that's not such a big deal). With individual indexes     you also have more flexibility in adjusting storage parameters.   

    Just curious what other people are doing or have to say.

    Thanks.

---

    David Hiltz
    dhiltz_at_whsun1.wh.whoi.edu
    Network System Administrator
    Northeast Fisheries Science Center
    ######&_at_&###### Received on Sat Oct 08 1994 - 15:58:05 CET