如何创建一个查询来获得使用where子句作为结果数组索引的结果？

Question

这是查询我使用：

$idList="32,33,21,11";   
$query = "SELECT post_id, meta_value FROM wp_posts 
      WHERE meta_key = 'grade' AND post_id IN ($idList)"; 

其结果是，在where子句变成键：

$result = array(
       0 => array('post_id'=> 32, 'meta_value'=>5), 
       1 => array('post_id'=> 33, 'meta_value'=>2), 
       2 => array('post_id'=> 21, 'meta_value'=>8), 
      ) 

我希望有这样的结果：

$result = array(
       0 => array(32 => 5), 
       1 => array(33 => 2), 
       2 => array(21 => 8), 
      ) 

如何为了达成这个？谢谢！

Answer 1

遍历结果集是这样的：

$_final = array(); // new result set 

foreach ($result as $value) 
    $_final[] = array($value['post_id'] => $value['meta_value']); 

unset($result); // free memory from old result set 

UPDATE：如果有太多的元素，你怕内存消耗，你可以做到这一点通过以下方式：

$_final = array(); // new result set 

foreach ($result as $key => $value) { 
    $_final[] = array($value['post_id'] => $value['meta_value']); // composing new data 
    unset($result[$key]); // unsetting already parsed value 
} 

unset($result); // freeing memory from old result set