问PHP -如何同时使用ORDER BY和GROUP BY

EN

我创建了一个包含message, sender, to, time的表，我希望按发件人分组和按时间排序这是我的代码

$query= mysql_query("SELECT * FROM  `table` ORDER BY `time` GROUP BY `sender`")or die(mysql_error());
while($arr = mysql_fetch_array($query)){
$num = mysql_num_rows($query);
$msg = $arr ['message'];
echo '</br>';
echo $msg;
}

这向我展示了这个错误

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'GROUP BY发件人' at line 1

那么如何解决这个问题呢？

谢谢

克劳斯