Cakephp计算平均问题

Question

我有这个问题:

   $this->set('grades', $this->Grade->Query("
SELECT AVG(grade), 
sections.section_name 

FROM grades, 
sections 

WHERE sections.id = grades.section_id 

AND grades.user_id =".$id." 

GROUP BY grades.section_id"));

我用它来输出数据:

<?php foreach($grades as $grade): ?>
    <tr>
        <td><?php echo $grade['Grade']['AVG(grade)']; ?></td>
    </tr>
<?php endforeach;?>

但它给了我一个"未找到警告指数等级".我怀疑这与它有关,['AVG(grade)']因为当我删除AVG(等级)时它输出正常(显然没有平均值)

有人可以提供帮助吗？

编辑

debug($grades) outputs:

Array
(
    [0] => Array
        (
            [0] => Array
                (
                    [avg_grade] => 4.75000
                )

            [sections] => Array
                (
                    [section_name] => Nederlands
                )

        )

    [1] => Array
        (
            [0] => Array
                (
                    [avg_grade] => 6.50000
                )

            [sections] => Array
                (
                    [section_name] => Engels
                )

        )

)

Answer 1

首先,debug( $grades )要查看平均值存储在数组结构中的位置.例如,您还可以在查询中将其命名为其他名称SELECT AVG( grade ) AS average.

作为旁注,您不需要使用原始查询(可能是偏好问题,但如果可能的话,我倾向于避免使用它们).你可以做

$this->Grade->find(
  'all',
  array(
    'conditions' => array(
      'Grade.user_id' => $id
    ),
    'recursive' => 1,
    'fields'    => array( 
      'AVG( Grade.grade ) AS average',
      // +whatever else you need
    )
    'group' => 'Grade.section_id'
  )
);

在这种情况下,当你做foreach( $grades as $grade )平均值将在$grade[0]['average'].