Bug #30553 subtraction from 0 not working correctly

• Submitted: 22 Aug 2007 4:08
• Modified: 22 Sep 2007 7:31
• Reporter: doug johnson
• Status: No Feedback
• Category: MySQL Server: Data Types
• Severity: S2 (Serious)
• Version: 4.1.19-standard
• OS: Linux (mysql-standard-4.1.19-pc-linux-gnu-i686-glibc23)
• CPU Architecture: Any

[22 Aug 2007 4:08] doug johnson

Description:
when I execute this query (via php):

update sometable set somefield = somefield + 1 where condition...

it work (increments somefield) and if I do:

update sometable set somefield = somefield - 1 where condition...

it works as well (subtracts 1 from somefield) except when somefield starts out as 0. when somefield starts out as zero the result is -2 instead of -1 as expected.

I did a workaround by doing:

update sometable set somefield = somefield +- 1 where condition...

but I am sure that other people would miss this if they didnt test their results properly.

How to repeat:

update sometable set somefield = somefield - 1 where condition...

will return -2 if somefield starts out == 0

Suggested fix:
update sometable set somefield = somefield +- 1 where condition...

will give the desired result when the initial value of somefield == 0

[22 Aug 2007 7:31] Hartmut Holzgraefe

Hi,

could you provide real CREATE, INSERT and UPDATE statements 
for this problem?

I can't reproduce this using generic tables and statements
so we need to know your exact setup for this ...

[22 Sep 2007 23:00] Bugs System

No feedback was provided for this bug for over a month, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".