PDO 的游标为何无效?

			$aa = $db->prepare('select * from user',array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));			$aa ->execute();			$aa->fetch();			$aa->fetch();			$a=$aa->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_NEXT);			print_r($a);

prepare中已经设置了开启游标;
结果是第三行,而不是最后一行;
测试了所有的fetch第二个参数,均无效;

求问这是什么原因,这个又不是回滚,需要表是INNODB吗?
按照手册上的写法,也不好用,很是费解;
求助中....thinks;

回复讨论(解决方案)

当然是第三行记录啦，你仔细看看手册上的例子以及函数的说明

FETCH_ORI_NEXT
Fetch the next row in the result set. Valid only for scrollable cursors.
取下一行的结果集

FETCH_ORI_PRIOR
Fetch the previous row in the result set. Valid only for scrollable cursors.
取前一行的结果集

FETCH_ORI_FIRST (integer)
Fetch the first row in the result set. Valid only for scrollable cursors.
取结果集中的第一行

FETCH_ORI_LAST
Fetch the last row in the result set. Valid only for scrollable cursors.
取最后一行的结果集

FETCH_ORI_ABS
Fetch the requested row by row number from the result set. Valid only for scrollable cursors.
获取所请求的行数从结果集

FETCH_ORI_REL
Fetch the requested row by relative position from the current position of the cursor in the result set. Valid only for scrollable cursors.
获取所请求的行从结果中光标当前位置的相对位置的设置