On Thu, 28 Feb 2002 15:32:24 +0100, Roger Baklund wrote: >As far as I can tell, there are at least two bugs. > >One bug is already known, it is the rounding error that applies to some >platforms, depending on the underlaying C library being used: > >win2k, 3.23.30-gamma: > >mysql> select round(1.5); >+------------+ >| round(1.5) | >+------------+ >| 1 | >+------------+ >1 row in set (0.00 sec) > >solaris, 3.23.39-log: > >mysql> select round(1.5); >+------------+ >| round(1.5) | >+------------+ >| 2 | >+------------+ >1 row in set (0.02 sec) > >This is... inconvenient. Even if the reason for the bug is the different C >library implementations, the result will be mysql applications with errors. >IMHO the developers should try to work around this, so that the round() >function works the same way on all platforms.
My experience with mysql doesn't go back very far. Thus, I excuse myself for missing the change in rounding behavior between versions. Now that I'm done "crawdadding"... I agree completely. :) >The other bug is related to the preparation of the statement. It seems the >number of decimals in the output column is decided once before the actual >query is performed, and this number is fixed: > >mysql> select *,round(num1,id) from tab4; >+------+----------+----------------+ >| id | num1 | round(num1,id) | >+------+----------+----------------+ >| 1 | 1.2345 | 1.2000 | >| 2 | 12.3456 | 12.3500 | >| 3 | 100.4235 | 100.4230 | >+------+----------+----------------+ >3 rows in set (0.01 sec) > >The parser tries to decide the number of decimals _before_ the query is >executed, but as 'id' does not make any sense at that point, the number of >decimals in the num1 parameter (4) is used... then, for each row, the >round() function is executed with the correct parameters, and the result is >"correct" (if we ignore the rounding error), but is then padded with zeroes, >so that the total number of decimals is four. This padding makes the result >wrong, as "1.2000" is not the same as "1.2" when we talk about human >readable numbers. (The first indicate a higher grade of precision.) > You're absolutely right on the matter of interpretation by humans and I failed to consider that when I concluded the display of the rounded values was acceptable. Problem was, we knew the original values and were not receiving them as the only set. But, I view this as a design oversight that should be addressed rather than as a bug. Doug --------------------------------------------------------------------- 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
