为何pdo的prepared statement不能用在order by和limit上？

$sql = "SELECT * FROM table ORDER BY :sort :dir LIMIT :start, :results";
$stmt = $dbh->prepare($sql);
$stmt->execute(array(
     'sort'  => $sort, 
     'dir'  => $dir, 
     'start'  => $start,
     'results' => $results,
     )
    );
var_dump($stmt->fetchAll(PDO::FETCH_ASSOC));

上面var_dump发现没有取回结果，这是什么原因？

问于 2010-04-21, 11:17

gossipgirl
2452

2 个答复

最早最新投票

这跟pdo没关系，而是因为DBMS本身不支持prepare对表名的处理：

mysql> PREPARE stmt1 FROM 'SELECT SQRT(POW(?,2) + POW(?,2)) AS hypotenuse';
mysql> SET @a = 3;
mysql> SET @b = 4;
mysql> EXECUTE stmt1 USING @a, @b;
mysql> EXECUTE stmt1 USING @a, @b;
+------------+
| hypotenuse |
+------------+
|          5 |
+------------+

参考资料：SQL Syntax for Prepared Statements