while循环只返回第一行的timediff

Code

$minus = mysql_query("SELECT * FROM dtr");
while($minusdata = mysql_fetch_array($minus, MYSQL_ASSOC))
{
    $time = mysql_fetch_assoc(mysql_query("SELECT time_to_sec(timediff(time_out,time_in)) as x from dtr where dtr_id = dtr_id"));
    $t = $time['x'];
    mysql_query("UPDATE dtr SET diff = '$t' WHERE dtr_id = dtr_id AND time_out != '00:00:00'");
}
$minus = mysql_query("SELECT * FR