Re: Where v. If in high hit rate tables

In Article<4efqh4$jgo@nic.ftns.no>, <Nils.Myklebust@ccmail.telemax.no> writes: > ... was often very true some years back, > particularly with Informix SE. The performance advantage even when the > hit rate wasn't very high gould be tremendous. I think that was to a > large extent due to the optimiser not selecting the best access path, > but may also have had several other reasons. > This is generaly no longer the case. > Actually, the version 5.x engine optimizer has never been fixed. It still exhibits abnormal selection of indexes. This is especially true of tables which are highly dynamic. That is, the number of rows changes significantly. No, UPDATE STATISTICS will not fix the problem. In fact, updating statistics on a table can kill performance. Sometimes a select within a loop is the best approach (until you add or delete a large percentage of records).