Bind_result不能在prepared（）查询中使用。

Question

我想在另一个查询中使用绑定结果中的变量但是我得到一个错误，说结果是非对象。

PHP Fatal error: Call to a member function bind_param() on a non-object in

$stmt =mysqli_prepare($link, "SELECT DISTINCT COL1 from TABLE1 WHERE COLID = ?");
$stmt->bind_param("s", $SOMEID);
$stmt->execute();
$stmt->bind_result($COL1);


while ($stmt->fetch()) {
            $stmt1 =mysqli_prepare($link, "SELECT COLA from TABLE2 WHERE COLID = ?");
            $stmt1->bind_param("s", $COL1);
            $stmt1->execute();
            $stmt1->bind_result($COLA);
            $stmt1->fetch();   
            if (!$COLA)
                    {
                    echo $COLA;    
                    }

                    }  

如何使用$COL1选择$COLA？