Roger,
You can always write your own Round() function and have it
round exactly the way you want.
To round up on a decimal digit 5 use:
mysql> select truncate(1.235+0.005,2) rounded;
+---------+
| rounded |
+---------+
| 1.24 |
+---------+
1 row in set (0.00 sec)
To round down on a decimal digit 5 use:
mysql> select truncate(1.235+0.0049,2) rounded;
+---------+
| rounded |
+---------+
| 1.23 |
+---------+
1 row in set (0.01 sec)
This should be faster than "(FLOOR((2.55*10)+0.5)/10)" and there is no
rounding error to worry about.
Brent
At 06:14 AM 3/1/2002 , you wrote:
>Hi,
>
>there are a couple of bugs related to the round() function. (See the thread
>'Can somebody help me with "round (columna,columnb) "?')
>
>One bug is already well known and documentet, it is related to different C
>library implementations on different platforms: the result of round(2.55,1)
>may be 2.5 or 2.6.
>
>The other bug is related to using a column name as the decimal parameter to
>the round() function (select round(col1,col2) from table). The rounding is
>performed, but the result is padded with zeroes, so that all rows have the
>same number of decimals. The number of decimals used is the number of
>decimals in the definition of col1, or if 'col1' is an expression, the
>highest number of decimals in any of the parameters in the expression. This
>is wrong, because "1.1000" indicates a higher grade of precision than "1.1",
>even if it has the same numeric value.
>
>While investigating this issue, I came across what I think is a third bug:
>
>solaris, 3.23.39-log:
>
>mysql> select round(0.5,0),round(0.55,1),round(0.555,2);
>+--------------+---------------+----------------+
>| round(0.5,0) | round(0.55,1) | round(0.555,2) |
>+--------------+---------------+----------------+
>| 0 | 0.6 | 0.56 |
>+--------------+---------------+----------------+
>1 row in set (0.00 sec)
>
>If 0.5 is rounded down to 0, why is 0.55 and 0.555 rounded up to 0.6 and
>0.56?
>
>I would have expected 0/0.5/0.55 or 1/0.6/0.56
>
>win2k, 3.23.30-gamma:
>
>mysql> select round(0.5,0),round(0.55,1),round(0.555,2);
>+--------------+---------------+----------------+
>| round(0.5,0) | round(0.55,1) | round(0.555,2) |
>+--------------+---------------+----------------+
>| 0 | 0.5 | 0.56 |
>+--------------+---------------+----------------+
>1 row in set (0.00 sec)
>
>On my win2k box 0.5 and 0.55 is rounded down, but 0.555 is rounded up...?
>
>Both my boxes agree on this:
>
>mysql> select round(0.55-0.5,1),round(0.05,1);
>+-------------------+---------------+
>| round(0.55-0.5,1) | round(0.05,1) |
>+-------------------+---------------+
>| 0.1 | 0.0 |
>+-------------------+---------------+
>1 row in set (0.00 sec)
>
>mysql> select 0.55-0.5=0.05;
>+---------------+
>| 0.55-0.5=0.05 |
>+---------------+
>| 0 |
>+---------------+
>1 row in set (0.00 sec)
>
>...but this is correct on both boxes:
>
>mysql> select 0.55-0.05=0.5;
>+---------------+
>| 0.55-0.05=0.5 |
>+---------------+
>| 1 |
>+---------------+
>1 row in set (0.00 sec)
>
>Another test:
>
>solaris:
>
>mysql> select round(0.05,1),round(0.15,1),round(0.25,1),round(0.35,1);
>+---------------+---------------+---------------+---------------+
>| round(0.05,1) | round(0.15,1) | round(0.25,1) | round(0.35,1) |
>+---------------+---------------+---------------+---------------+
>| 0.0 | 0.2 | 0.2 | 0.4 |
>+---------------+---------------+---------------+---------------+
>1 row in set (0.00 sec)
>
>Sometimes it rounds up, sometimes it rounds down...
>
>win2k:
>
>mysql> select round(0.05,1),round(0.15,1),round(0.25,1),round(0.35,1);
>+---------------+---------------+---------------+---------------+
>| round(0.05,1) | round(0.15,1) | round(0.25,1) | round(0.35,1) |
>+---------------+---------------+---------------+---------------+
>| 0.0 | 0.1 | 0.2 | 0.3 |
>+---------------+---------------+---------------+---------------+
>1 row in set (0.00 sec)
>
>Always down, that could be ok, but...:
>
>mysql> select round(0.005,2),round(0.015,2),round(0.025,2),round(0.035,2);
>+----------------+----------------+----------------+----------------+
>| round(0.005,2) | round(0.015,2) | round(0.025,2) | round(0.035,2) |
>+----------------+----------------+----------------+----------------+
>| 0.00 | 0.01 | 0.02 | 0.04 |
>+----------------+----------------+----------------+----------------+
>1 row in set (0.00 sec)
>
>Can anyone confirm if this behaviour is also in the newer versions?
>
>Please tell me if there is something wrong with my expectations...
>
>--
>Roger
>query
>
>
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