Q: Estimated Cost from SET EXPLAIN?

Attached is the actual output from our problem site and a brief explanation of what is happening. If you could post this (and show me where and how you post such questions), I would appreciate it. Let me know. The 'sqexplain.out' output follows. Thanks. PROBLEM: The following 'sqexplain.out' output relates to slightly different select statements. QUERY_1 represents output from a select statement employing a "from occupant, directory" approach, yielding an "Estimated Cost" which appears to be "appropriate" but produces a "SEQUENTIAL SCAN". QUERY_2 represents output from a select statement employing a "from directory, occupant" approach, yielding an "Estimated Cost" which is negative but appropriately utilizes the index which exists for the directory table (which does not appear to help). QUERY_1 and QUERY_2 selects are about the same speed at one particular site, but at all other sites, QUERY_2 is a much faster select (less than 1-second vs. 7-10 seconds), AND, always produces a positive "appropriate" "Estimated Cost" value. QUESTION: Does a negative "Estimated Cost" value indicate that there can be a problem with the database and/or select methodology? and if so, what kind of problems and how can they be rectified? QUERY_1: -------- select entryid, entrytype, aux, lastname, firstname, midname, linenum, dirline, length(room) rmlen, room from occupant, directory where occupant.room="2701P" and directory.entryid=occupant.occid Estimated Cost: 893 Estimated # of Rows Returned: 2 1) acs.directory: SEQUENTIAL SCAN 2) acs.occupant: INDEX PATH Filters: acs.occupant.room = '2701P' (1) Index Keys: occid Lower Index Filter: acs.occupant.occid = acs.directory.entryid QUERY_2: -------- select entryid, entrytype, aux, lastname, firstname, midname, linenum, dirline, length(room) rmlen, room from directory, occupant where occupant.room="2701P" and directory.entryid=occupant.occid order by rmlen, room, lastname, firstname, midname, entryid, linenum Estimated Cost: -11230 Estimated # of Rows Returned: 2 Temporary Files Required For: Order By 1) acs.occupant: INDEX PATH (1) Index Keys: room Lower Index Filter: acs.occupant.room = '2701P' 2) acs.directory: INDEX PATH (1) Index Keys: entryid Lower Index Filter: acs.directory.entryid = acs.occupant.occid GRFollis (follis@esd.dl.nec.com) -- -------------------------------------------------------------------------- The most widely used computer language .... $*#%"&@+! --------------------------------------------------------------------------