SQL error of MySQL

[wxdqz]

Hi,
this is my table (Logs)
Logs (
LogsID timestamp(14),
date date,
nom varchar(16),
prenom varchar(16),
fichier varchar(32),
profession varchar(32),
adresse varchar(255),
cp varchar(16),
ville varchar(32),
pays int(8),
tel varchar(16),
fax varchar(16),
ip varchar(16),
host varchar(64),
Email varchar(130),
TFichierID int(8),
flag tinyint(1) DEFAULT '0',
KEY logsID (LogsID)
)

when i send this query:
UPDATE Logs set flag='0';

i got all field flag at 0 ok, but it modify The LogsID field too !
why ???
i cannot understand
please help