Re: SQL Optimizer

Posted in 1997

David Williams — Sat, 22 Mar 1997 23:34:49 +0000 — source: Informix-list mailing list archive (1991-1998)

In article <5h0rfk$qq2@cssun.mathcs.emory.edu>, Emil Sarkissian <semil@comm.uni-svishtov.bg> writes >Does anyone know what "Estimated Cost" really >means, when the sqexplain.out file is generated >by OnLine 5.1? > >When I add silly conditions like: > >SELECT ps.ln > WHERE ps.sheet_date BETWEEN BeginDate AND EndDate > AND ps.ln = ps.ln -- ??? cost goes down ???> >the cost moves goes down... > >BTW Is there a comprehensive explanation of HOW >the optimizer makes its decisions? Check the SQL manuals.... -- David Williams