Did you gave a try on using coalesce in your query? ""Jerry Schwartz"" <jschwa...@the-infoshop.com> escreveu na mensagem news:02a201cac083$e07a2330$a16e69...@com... > >-----Original Message----- >>From: João Cândido de Souza Neto [mailto:j...@consultorweb.cnt.br] >>Sent: Wednesday, March 10, 2010 10:55 AM >>To: mysql@lists.mysql.com >>Subject: Re: Particular value or NULL >> >>Maybe: >> >>WHERE coalesce(x, 17) = 17 >> >> > [JS] Interesting suggestion, but > > us-gii >select benchmark(10000000,(7=7 or null is null)); > +-------------------------------------------+ > | benchmark(10000000,(7=7 or null is null)) | > +-------------------------------------------+ > | 0 | > +-------------------------------------------+ > 1 row in set (0.34 sec) > > us-gii >select benchmark(100000000,coalesce(null,7)); > +---------------------------------------+ > | benchmark(100000000,coalesce(null,7)) | > +---------------------------------------+ > | 0 | > +---------------------------------------+ > 1 row in set (2.61 sec) > > It looks like COALESCE() is slower. Of course this isn't anything like a > real > test. Among other things, I have no idea how well or poorly the optimizer, > query cache, etc. handle it. I don't know how much magic there is in the > BENCHMARK() function, either. I would hope that the server would know that > the > expression needs to be evaluated over and over again from scratch. > > Regards, > > Jerry Schwartz > The Infoshop by Global Information Incorporated > 195 Farmington Ave. > Farmington, CT 06032 > > 860.674.8796 / FAX: 860.674.8341 > > www.the-infoshop.com > > > > >>""Jerry Schwartz"" <jschwa...@the-infoshop.com> escreveu na mensagem >>news:023301cac069$366afa00$a340ee...@com... >>> Is there a better construct for the WHERE clause in a LEFT JOIN than >>> >>> >>> >>> WHERE (x = 17 OR x IS NULL) >>> >>> >>> >>> ? >>> >>> >>> >>> Regards, >>> >>> >>> >>> Jerry Schwartz >>> >>> The Infoshop by Global Information Incorporated >>> >>> 195 Farmington Ave. >>> >>> Farmington, CT 06032 >>> >>> >>> >>> 860.674.8796 / FAX: 860.674.8341 >>> >>> >>> >>> <http://www.the-infoshop.com> www.the-infoshop.com >>> >>> >>> >>> >> >> >> >>-- >>MySQL General Mailing List >>For list archives: http://lists.mysql.com/mysql >>To unsubscribe: http://lists.mysql.com/mysql?unsub=jschwa...@the- >>infoshop.com > > > >
-- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=arch...@jab.org
