Doctrine 2：按字段分组（错误：'...'不指向类。） [英] Doctrine 2: group by field alias (Error: '...' does not point to a Class. )

问题描述

我得到这个Doctrine查询：

I got this Doctrine query:

        select upper(substring(e.name, 1, 1)) first_letter
        from Application\Models\Exercise e
        group by first_letter
        order by first_letter asc

但是它会引发一个异常：消息：

But it throws an exception with the message:

Error: 'first_letter' does not point to a Class. 

如果我通过省略 订单由，它的工作原理。

If I leave out the group by and the order by, it works.

在这种情况下，我必须使用本地查询，或者在客户端代码中进行排序和分组（根据数据量的大小可能不是一个好主意）数据库...）或者是否可以让这个查询工作？

Do I have to use a native query in this case or do the sorting and grouping in my client code (probably not such a good idea depending on the amount of data in the db...) or is it possible to get this query working?

谢谢！

编辑：

这是我目前的做法，不是很好，但是暂时工作，因为没有太多的数据db：

This is my current approach, not so nice, but works for the moment as there is not much data in the db:

    $tmpResult = $this->getEntityManager()->createQuery('
        select upper(substring(e.name, 1, 1)) first_letter
        from Application\Models\Exercise e
    ')->getResult();

    $groupedAndSortedResult = array();

    foreach($tmpResult as $row) {
        $groupedAndSortedResult[$row['first_letter']] = $row['first_letter'];
    }

    sort($groupedAndSortedResult);

    return array_values($groupedAndSortedResult);

推荐答案

我知道你自己回答了这个问题，想知道你是否尝试使用 DISTINCT ：

I know you've answered this question yourself but just wondering if you tried using DISTINCT:

select DISTINCT upper(substring(e.name, 1, 1)) first_letter
from Application\Models\Exercise e    
order by e.name asc

订购 e.name 相当于 first_letter 在这种情况下。

Ordering by e.name is equivalent to first_letter in this case.

这篇关于Doctrine 2：按字段分组（错误：'...'不指向类。）的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！