Zend\Db:从子查询中选择 [英] Zend\Db: Select from subquery

问题描述

我正在将一个应用程序从 ZF1 移植到 ZF2，作为其中的一部分，我必须重写我们的数据库映射器.

I'm porting an application from ZF1 to ZF2 and as part of that I have to rewrite our database mappers.

我正在为这个 SQL 语句苦苦挣扎:

I'm struggling with this SQL statement:

SELECT full_name, GROUP_CONCAT(value)
FROM (
   SELECT full_name, value
   FROM my_table
   ORDER BY id DESC
   ) as subtable
GROUP BY full_name
ORDER BY full_name DESC;

我试图解决的根本问题是我需要在运行 GROUP_CONCAT 之前对子查询的结果进行排序，并且我需要它同时适用于 MySQL 和 Sqlite.在 MySQL 中，我可以简单地在 GROUP_CONCAT 函数中指定顺序，但这在 Sqlite 中是不可能的，所以我需要子查询才能与 MySQL 和 Sqlite 兼容.

The underlying problem I'm trying to solve is that I need to order the results of the sub query before running GROUP_CONCAT and I need it to work for both MySQL and Sqlite. In MySQL I could simply specify the order within the GROUP_CONCAT function, but this is not possible with Sqlite so I need the sub query for it to be compatible with both MySQL and Sqlite.

在 ZF1 中我可以做到:

In ZF1 I could do:

$fromSql = $db->select()
              ->from('my_table', array('full_name', 'value'))
              ->order('id DESC');

$sql = $db->select()
          ->from(array(
                'subtable' => new Zend_Db_Expr('(' . $fromSql . ')')
            ), array(
                'full_name' => 'full_name',
                'value' => new Zend_Db_Expr('GROUP_CONCAT(subtable.value)'),
            )
          )
          ->group('full_name')
          ->order('full_name DESC');

但是，ZF2 似乎无法在 from 子句中使用子查询.有没有办法解决这个问题?

However, using a sub query in the from clause doesn't seem possible with ZF2. Is there some work around for this?

推荐答案

EDIT:实际上，我现在发现我的查询存在缺陷.它不会在 MySQL 中按预期工作，这意味着我仍然必须编写专门的查询.请参阅GROUP_CONCAT 更改 GROUP BY 顺序

EDIT: Actually, I now see that my query was flawed. It won't work as expected with MySQL, which means I still have to write specialized queries. See GROUP_CONCAT change GROUP BY order

经过Zend\Db\Sql\Select 的代码后，我发现了以下几行:

After going through the code of Zend\Db\Sql\Select I found these lines:

if ($table instanceof Select) {
    $table = '(' . $this->processSubselect($table, $platform, $driver, $parameterContainer) . ')';
} else {
    $table = $platform->quoteIdentifier($table);
}

所以答案其实很简单，我所要做的就是向 from() 提供一个 Zend\Db\Sql\Select 对象，而不用包装它在 Zend\Db\Sql\Expression 中，就像我以前使用 ZF1 一样.

So the answer is actually quite simple, all I had to do was to provide a Zend\Db\Sql\Select object to from(), without wrapping it in a Zend\Db\Sql\Expression like I used to with ZF1.

代码示例:

$adapter = $this->getAdapter(); // Returns Zend\Db\Adapter\Adapter
$sql = new Zend\Db\Sql\Sql($adapter);

$from = $sql->select()
    ->from(static::$table)
    ->columns(array(
        'full_name',
        'value',
    ))
    ->order('id DESC');

$select = $sql->select()
    ->from(array(
        'subtable' => $from,
    ))
    ->columns(array(
        'full_name' => 'full_name',
        'value' => new Expression('GROUP_CONCAT(value)'),
    ))
    ->group('full_name')
    ->order('full_name DESC');

$selectString = $sql->getSqlStringForSqlObject($select);

$resultSet = $adapter->query($selectString, $adapter::QUERY_MODE_EXECUTE);

return $resultSet->toArray();

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