Bug #3019 timestamp column auto update when updating other column
Submitted: 1 Mar 2004 1:44 Modified: 1 Mar 2004 6:30
Reporter: Liu Naijia Email Updates:
Status: Not a Bug Impact on me:
None 
Category:MySQL Server Severity:S1 (Critical)
Version:4.1.1-alpha-max OS:Linux (RedHat 7.3)
Assigned to: CPU Architecture:Any

[1 Mar 2004 1:44] Liu Naijia 
Description:
when timestamp column "A" uses default value 'now()' and you update another column B,the value of "A" will be updated to 'now()'

How to repeat:
create table test (
    v1 timestamp default 'now()',
    v2 timestamp
);

insert into test(v2) values(now());

update test set v2 = now();

you will see 
   value of v1 =  value of v2
[1 Mar 2004 6:30] MySQL Verification Team 
Thank you for writting to us.

This is documented behaviour. First timestamp column in the table is ALWAYS
updated when a row is written.