OPTIMISATION of SELECT statement

I am writing an application for a client (Informix 4gl) which will require a very large SELECT using a number table joins (up to 12 - each table having a large volume of data, approx 200,000 rows each ) and a wide variety of selection criteria. My question is - will it be more efficient to do this selection in one SELECT statement, or break the query down into several SELECT statements, using temporary tables etc. If I go for the "one select" option, is the access time from the database faster depending on the order of the tables in the FROM clause ? Any suggestions ? Trish Trish Paragon Group Dublin ------------000----------000------------000---------000---------