In the last episode (Nov 18), Ahmad Al-Twaijiry said: > I have a column in a table defined as float > > mynumber float(20,2) > > if we say mynumber column in a row is 1000000 , when I run this SQL : > > UPDATE Table SET mynumber=mynumber-100.15 > > the mynumber column will be 999900 not 999899.85 > > what is the problem ?
It works for me (approximately) in mysql 5.1: mysql> create table blah ( mynumber float(20,2) ); mysql> insert into blah values ( 1000000 ); mysql> update blah SET mynumber=mynumber-100.15; mysql> select * from blah; +-----------+ | mynumber | +-----------+ | 999899.88 | +-----------+ 1 row in set (0.02 sec) Since base-10 fractions can't be represented exactly by a base-2 floating-point number, any fractional value you store will be imprecisely stored and will cuase rounding errors. You probably want to use the DECIMAL type instead of FLOAT. http://dev.mysql.com/doc/refman/5.0/en/numeric-type-overview.html -- Dan Nelson [EMAIL PROTECTED] -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
