== Quote from evanpeck ( evanpeck@gmail.com)'s article
> I'm not really sure if my problem lies in the PHP code or the SQL...
> but here it is:
> begin();
> $query = "UPDATE Nodes "
> ."SET NodeStatus = 1 "
> ."WHERE NodeID = $NodeID AND NodeStatus = 0";
> $result = mysql_query($query);
> if ($result == null || $result == false) {
> rollback();
> return;
> }
> In the Nodes table, there should be only one instance of a node with
> a
> particular NodeID.
> So, presumably, user1 will hit the UPDATE and change the NodeStatus
> to
> 1. Then, when user2 hits the UPDATE, it should fail, since the
> NodeStatus =1 (and a condition of the update is that the NodeStatus
> =0).
> However, when multiple users simultaneously (at least down to the
> second, according to logs) access the method, they ALL succeed in the
> UPDATE query. I don't understand how this can happen. I'm assuming
> that the UPDATE operation is atomic in mySQL.
> I feel like I shouldn't have to use locks.. but I'm considering it
> with the terrible results so far.

you don't need to consider locks; however, you do need to look at your isolation
level. can you tell us what is the isolation level of mysql server. it can be
found in the my.cnf .

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