Re: Database design question

In article <329854CA.45D@netcomuk.co.uk>, Neil Truby <ntruby@netcomuk.co.uk> writes >Thanks to those who responded to my specific query last time. I'm going >to ask the same question in the abstract: > >say I have a table with a million rows. One column is an indicator, >which will almost always be null. However, it is *very* important to be >able to quicly identify the 5 rows (out of the million) that have the >indicator set. Some DBMSs, Adabas for example, would allow the column >to be set up as a "null-suppressed index", that is, only non-null values >would have an index entry built for them. This is extremely efficient. > >How would you do it in a relational design? > >Thanks >Neil Truby >Chase Bank >Bournemouth, UK You can not. The best method for highly duplicate values is Sybase's bit-wise indicies (Gulp! Sorry - had to say it as it it true). Informix will have them in later releases. -- David Williams