Re: Is this a Bug??? Opinions wanted

William you made the point in your last statement "different optimizer settings, variations on "update statistics", and so forth can and often do lead to amazingly different paths the query can take" The point here: KNOW HOW to read the EXPLAIN OUTPUT and make corrections in YOUR CONFIGURATION or INDEXES that BEST SUIT YOUR SYSTEM USAGE OF that DATA. In my Informix DBA classess point of one of these was made: Customer XYZ called because it was taking X hours to execute a simple query. They created Indexs and had a table with X million rows (followed all the design rules), just could not understand why it was taking so long! HUM!!! They NEVER RAN AN UPDATE STATISTICS!!! For those of you who do not know what that statement does: It supplies the Optimizer of the Engine with the Statistical DATA it NEEDS to FIGURE out the BEST QUERY PATH....... ------------------------------------------------------------------------- Cheryl Kendricks Internet:cherylk@prod1.jcdc.doleta.gov OR cherylk@gwysmtp.jcdc.doleta.gov DTSI, Inc. Database Administrator - DOL Job Corps San Marcos, Texas ------------------------------------------------------------------------ On 21 Jun 1996, William Harris wrote: > In article <4q9kmo$dhu@mule1.mindspring.com>, barryleb@atl.mindspring.com > says... > >Below is the set explain output from two very similar queries. Please > >look carefully at the SQL. These queries do return different results. > >Should they? We have differing opinions within our database team. > > You're saying that the actual output of this query, from the same input data, > is different between the two identical select statements? I would welcome a > logical explanation of why a query in a relational database can return two > different results; an RDBMS is ultimately based on a rather strict mathematical > model. > > The "explain" output, I find the first one rather goofy but different optimizer > settings, variations on "update statistics", and so forth can and often do lead > to amazingly different paths the query can take. > -- > William Harris william@carsinfo.com > CARS Information Systems > 4000 Executive Park Drive > Cincinnati, OH (USA) 45241 > >