Re: sql question

In <27o4ejINNdfs@emory.mathcs.emory.edu> inf_bb@hermes1.sps.mot.com (Bob Baskett) writes: >netters, >can someone explain why the optimizer doesnt short circuit on the following >query: > > QUERY: > ------ > select * > from book_bill_back > where 1=2> > > Estimated Cost: 370832 > Estimated # of Rows Returned: 4330952 > > 1) book_bill_back: SEQUENTIAL SCAN > > Filters: 1 = 2 This is treated as WHERE <expression> = <expression>. The optimiser assumes that an expression is likely to be variable and hands it off to the engine. In some ways this behaviour is reasonable, after all *you* should know whether 1 = 2, the optimiser doesn't expect you to be daft enough to say WHERE <constant> = <constant> !!! :-) graeme -- Disclaimer: The author's opinions are his own, and not necessarily those of Pyramid Technology Ltd. or Pyramid Technology Inc. --------------------------------------------------------------------------- -m------- Graeme Sargent Voice: +44 (0)252 373035 ---mmm----- Senior Database Consultant Fax : +44 (0)252 373135 -----mmmmm--- Pyramid Technology Ltd. Telex: Tell who??? -------mmmmmmm- Farnborough, Hants GU14 7PL Email: graeme@pyra.co.uk --------------------------------------------------------------------------- We have the technology. The tricky bit is learning how to use it.