$address=M('address');
$addresslist['userid']=trim($_SESSION['id']);
$addresslist['province']=trim($_REQUEST['province']);
$addresslist['city']=trim($_REQUEST['city']);
$addresslist['address']=trim($_REQUEST['address']);
$addresslist['code']=trim($_REQUEST['code']);
$addresslist['name']=trim($_REQUEST['name']);
$addresslist['tel']=trim($_REQUEST['tel']);
if($address->create($addresslist))
{
$addressid=$address->where('userid='.$_SESSION['id'])->field('id,userid')->find();
if($_SESSION['id']==$addressid['userid'])
{
$address->where('userid='.$_SESSION['id'])->save();
}else{
$address->add();
}

}else{
$this->error('失败');
}
如果我把$addressid=$address->where('userid='.$_SESSION['id'])->field('id,userid')->find();
if($_SESSION['id']==$addressid['userid'])去掉就成修改数据库第一条。