Re: Tuning of a query...

Hi, in general, such query-"re-prositioning" will not influence optimizer decisions. However, with directives you can excert such influence. Please see the manual "Performance Guide" for more information on "Optimizer Directives". As well, you can check what exactly the optimizer does (and thus whether there would be any change in your example) by using the "SET EXPLAIN ON" statement. This will write information about the query execution plan, cost estimates, etc. into a local file (usually named "sqexplain.out"). Regards, Martin -- Martin Fuerderer IBM Informix Development Munich, Germany Data Management Solutions owner-informix-list@iiug.org wrote on 02.12.2004 12:55:17: > Hi All, > > Does it improve the performance if we change the table position and join orders? For ex: > > SELECT * > FROM table1 a, table 2 b > WHERE a.col1 = b.col2 > AND a.col2 = b.col2> > Ie, if table1 has more data than table2? If we interchange the positions?. Does it improve the performance? > Similarly changing the order of the joined columns? > > Or does the Informix optimizer is smart enough to take care of this??? Plz let us know regarding this? > > Vijay Kumar. R sending to informix-list