PHP PDO Oracle 问题 （急：在线等）

代码：
 $tns = "  
(DESCRIPTION =(ADDRESS_LIST =(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.11.200)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.11.200)(PORT = 1521))(LOAD_BALANCE = yes)(FAILOVER = ON))(CONNECT_DATA =
(SERVICE_NAME = orcl)))
  ";
$dbh = new PDO("oci:dbname=".$tns.";charset=utf8","ocp","ocp");

$sql_0 = "SELECT GAMEID FROM OCP_BASEINFO_GAME WHERE gamename = '傲视天地'";
//$sql_1 = "select count(gamename) from OCP_BASEINFO_GAME";

$rs = $dbh->query($sql);
$result_arr = $rs->fetch();
print_r($result_arr);

以上为代码；
问题：sql_0 这一条sql执行到 $result_arr = $rs->fetch(); 时报错，而$sql_1能正确执行取得数据。
错误：Fatal error: Call to a member function fetch() on a non-object in E:\WorkSpace\HelloWorld\view\oracle.php on line 53

怎么没人回啊，求高手啊！