As with everything in databases, performance depends on what you're doing. (What follows is general database information, not Derby specific.) If you have a query like:
select bannerbannerid from SSiteRequest where BANNERBANNERID=6 and WEBSITESWEBSITEID=10 and USERSUSERID=1 then the composite index will probably be faster. However, if your statements are like: select bannerbannerid from ssiterequest where useruserid=3 then the second index scheme will work better. In fact, in this example, the first index couldn't be used at all because it's not the first field in the index. (Which isn't always strictly true anymore. I know Oracle can use secondary fields like a primary field in some situations.) ry > > > Hi > Thank you very much for reading my post. > can you please explain me what is differences between 1 index for one > column and one index for multiple columns ? > in both performance view and technical differences. > > example : > > > create index Index1 on SSiteRequest (BANNERBANNERID, WEBSITESWEBSITEID, > USERSUSERID); > and > > create index Index13 on SSiteRequest (USERSUSERID); > create index Index12 on SSiteRequest (WEBSITESWEBSITEID); > create index Index1 on SSiteRequest (BANNERBANNERID); > > > does this two kind differ from each other ? > which one will have better performance? > > >
