Query Optimization question

Hi. What statistical information can Informix draw upon to determine how many rows will be satisified by a query coondition of the form "column = value", for example, "department = 'D'" where "department" may or may not be an "indexed" column. Where is this statistical information stored and what is the mechanism for keeping it up-to-date. Thankx in advance. Ignatius. iggycoco@pacbell.net P.S. If possible please copy me when posting a reply.