Hi! > but there are seperate indexes on column PREF, FLAG and SEX. > when those indexes are used ,cost=999. > > whereas when IDX_PROFILE_SHINKI ( a composite index on ENTPC, > FLAG,SEX,PREF,ENTDAY) is used , cost=7. > > 1.whys there is a huge difference in COST ?
As Wolfgang said, since your IDX_PROFILE_SHINKI index is unanalyzed, CBO is using default values, which look quite sexy costwise. Are your other indexes analyzed? > 2.does it mean that a composite index is better than individual ones ? Always depends. But I use them a lot. Optimizerwise - they might be bigger in sense of bytes & blocks, but again if they contain all columns required in qurey, that no table access is required, they can speed up lookups & short range scans significantly. Tanel. > > Kindly throw some light on this. > > Regards, > Jp. > > > > > > -- > Please see the official ORACLE-L FAQ: http://www.orafaq.net > -- > Author: Prem Khanna J > INET: [EMAIL PROTECTED] > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > San Diego, California -- Mailing list and web hosting services > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB ORACLE-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). > -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Tanel Poder INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
