Re: informix does not use indexes?

ProzessDV wrote in message <19981022044515.03961.00004046@ng34.aol.com>... >OWS 7.22 on SCO UNIX: > >The following SELECT-statement in dbaccess takes a long time until I get a >result , although I have declared an index on col4 (the table "table" has about >400000 rows). But when I use "set explain on" and look at the output of this >statement, I see that there is no index used for the search, just SEQUENTIAL >SCAN. I also tried to set optimization high or low. > >select * from table where col4 = 2> >Are there any options to set so that informix uses indexes, maybe? Firstly, does the optimiser have current information about the index; ie have you run an UPDATE STATISTCS recently? Even if you have, the index may not be a good candidate for use. If there are comparatively few distinct values for the index (male or female is a classic example) it will be quicker to use a sequential scan than use the index. Neil Truby aracnet Limited Weybridge, UK