Re: indexing

tomcaml@yahoo.com (tomL) wrote in message news:<3158a6a2.0408301033.2b1ab17b@posting.google.com>... > hello all! > > a few indexing questions: > > If the columns I filter on in my query are a subset of the columns in > an index, will the index be used? > > Also -- does the order in which the columns are specified in my filter > matter? > > thank you > tom given index create index mytable_1x on mytable(a,b,c); If you don't include at least the "a" column then it won't use the index. The other columns are optional but because you created a compound index you expect to know a,b,c more often or not. Another use is to get C quickly if you know A and B. select C from mytable where a=4 and b=5 ; This is because the optimizer will only look at the index for the information, since it has all of the information needed for the query.