Presence stop working after the table rosterusers has been modified.

Dear All,

I have modified the table rosterusers by this following sql script :

INSERT INTO rosterusers(username,jid,nick,ask,askmessage,server,subscription) values(USER_NAME, T.username||'@'||DOMAIN,'','N','','','B');

and after that all the users cannot retrieve other's presence from the server unless i restart the server.
Could you plz tell what is the cause of this problem ?

Thanks.