You are less likely to run into the issue when there are no calculations involved, but I wouldn't guarantee it. If you want to be on the safe side when using floating pont, do not check for EQUAL to, but within a range (+/- some small delta). As a rule of thumb, avoid floating point except for situations where you really need to represent very small fractions or extremely large numbers with less than 100% accuracy, or for real number math application (engineering, science).
Regards, Tore. ----- Original Message ----- From: "Stitchin'" <[EMAIL PROTECTED]> To: "Tore" <[EMAIL PROTECTED]> Sent: Friday, February 21, 2003 5:35 PM Subject: RE: decimal type > OH THANK YOU SO MUCH for that info!!! My first little database I created > today in mySql, I used that floating stuff on two columns, but they are only > to hold the height and width of my embroidery designs ... so I want to be > able to enter 3.25 (as in inches) and 10.12 etc... I'm not planning on > calculating with the fields, they're really just there for people to view > and search on .... if their embroidery machine can't do a design bigger > than 4" x 4" they can search and make sure those width and height columns > don't exceed 4". > > So is my usage of float ok? > > Renee :) > > -----Original Message----- > From: Tore [mailto:[EMAIL PROTECTED] > Sent: Friday, February 21, 2003 5:29 PM > To: mysql > Subject: Re: decimal type > > > Floating point should not be used for money or for representing any other > discrete numeric values. You will get in trouble because the floating point > value can deviate from the discrete value it is intended to represent. > Floating point introduces (small) rounding errors. > > Say an account has a balance of $265.50 and the user wants to withdraw the > entire amount, if your code checks that the withdrawal amount is less or > equal to the balance, it MAY not allow the withdrawal. Depending on how the > original value was established, you could see something like: > > In the table AccountBalances > > AccountID = 999 > Balance = 265.499999967 (value for illustration purposes only) > > Application screen shows two decimals: > Balance = $265.50 > > Customer withdrawal amount: $265.50 > > Query (or application logic with floating point values) that includes a > balance check: > > UPDATE AccountBalances > SET Balance = Balance - 265.50 > WHERE AccountID = 999 > AND Balance >= 265.50 > > This will affect 0 rows, which your code is smart enough to determine > meaning "insufficient funds". > > So, the moral of this story is to use fixed precision numerical values to > store information such as money... :-> > > HTH, > Tore. > > > ----- Original Message ----- > From: "Stitchin'" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Friday, February 21, 2003 5:00 PM > Subject: RE: decimal type > > > > Why couldn't you use float(10,2) ... just an example ... where the first > > number in the parentheses is the total characters for the number and the > > second number represents how many of those are right of the decimal > point?) > > > > I'm a TOTAL newbie to this stuff, I just set up my first mySql database > > today ... so I hope I'm not too far off base. > > > > Renee > > Stitchin' Up A Storm > > > > -----Original Message----- > > From: Bryan Koschmann - GKT [mailto:[EMAIL PROTECTED] > > Sent: Friday, February 21, 2003 4:01 PM > > To: gerald_clark > > Cc: [EMAIL PROTECTED] > > Subject: Re: decimal type > > > > > > My Apologies, > > > > table name is pricelist with 2 colums: > > create table pricelist (product varchar(45), cost dec); > > > > > > then > > > > load data infile "/home/omni/OmniPrice.csv" into table pricelist fields > > terminated by ','; > > > > the datafile looks like this > > > > Jaton Modem,15.5 > > Teac Floppy,7.5 > > Celeron 1.7,54.5 > > Logitech KB,11 > > > > > > but a query returns this: > > > > mysql> select * from pricelist; > > +-------------+------+ > > | product | cost | > > +-------------+------+ > > | Jaton Modem | 15 | > > | Teac Floppy | 7 | > > | Celeron 1.7 | 54 | > > | Logitech KB | 11 | > > +-------------+------+ > > 4 rows in set (0.00 sec) > > > > > > I read the docs on the decimal type, but I dont quite understand it. > > > > Thanks, > > > > Bryan > > > > > > On Fri, 21 Feb 2003, gerald_clark wrote: > > > > |Show us. > > |We have no idea how you defined your tables, > > |loaded your data, or structured your query. > > | > > |Bryan Koschmann - GKT wrote: > > | > > > > > > > > > > --------------------------------------------------------------------- > > 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 > > > > > --------------------------------------------------------------------- > 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
