MySQL manual A.5.7 Problems with floating point comparison =dn
----- Original Message ----- From: "Gerald Clark" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: 08 February 2002 15:24 Subject: Re: Problems with select > 15.8 has no exact binary representation, so a test for equality will fail. > Do not use floating point if you want to test for equality. Try DECIMAL > > Miguel Figueiredo wrote: > > >Hello all, > > > >I have a (probably dumb) question. > >My table "temperatura" has two fields described bellow. > > > >mysql> describe temperatura; > >+-------------+----------+------+-----+---------+-------+ > >| Field | Type | Null | Key | Default | Extra | > >+-------------+----------+------+-----+---------+-------+ > >| datetime | datetime | YES | | NULL | | > >| temperatura | float | YES | | NULL | | > >+-------------+----------+------+-----+---------+-------+ > >2 rows in set (0.00 sec) > > > > > >When I try to select rows with floats, the result is an empty set. > >For example: > > > >mysql> select datetime,temperatura from temperatura where > >datetime="2002-02-08 09:30:00"; > >+---------------------+-------------+ > >| datetime | temperatura | > >+---------------------+-------------+ > >| 2002-02-08 09:30:00 | 15.8 | > >+---------------------+-------------+ > >1 row in set (0.00 sec) > > > >----------------------------> got one row :) > > > >mysql>select datetime,temperatura from temperatura where datetime="2002-02-08 > >09:30:00" and temperatura=15.8; > > > >Empty set (0.00 sec) > > > >----------> same thing but with the temperatura value, gives me an empy set :( > > > >When I try to select another row but the temperatura field has an integer > >this is what happens: > > > >mysql> select datetime,temperatura from temperatura where > >datetime="2002-01-25 09:40:00"; > >+---------------------+-------------+ > >| datetime | temperatura | > >+---------------------+-------------+ > >| 2002-01-25 09:40:00 | 16 | > >+---------------------+-------------+ > >1 row in set (0.00 sec) > > > >-----------> got one row :) > > > >mysql> select datetime,temperatura from temperatura where > >datetime="2002-01-25 09:40:00" and temperatura=16; > >+---------------------+-------------+ > >| datetime | temperatura | > >+---------------------+-------------+ > >| 2002-01-25 09:40:00 | 16 | > >+---------------------+-------------+ > >1 row in set (0.00 sec) > > > >--------------> It works now :/ > > > >Does anyone have an idea why this happens? How can I select float numbers? > > > >Best wishes, > > > >Miguel > > > > > > --------------------------------------------------------------------- > Before posting, please check: > http://www.mysql.com/manual.php (the manual) > http://lists.mysql.com/ (the list archive) > > To request this thread, e-mail <[EMAIL PROTECTED]> > To unsubscribe, e-mail ><[EMAIL PROTECTED]> > Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php > > --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
