使用子句2 DBAL加入子查询

Question

我正在重构Zend Framework 2 应用程序，以使用准则2.5 DBAL代替Zend_DB（ZF1）。我有以下Zend_Db查询：

$subSelect = $db->select()
    ->from('user_survey_status_entries', array('userSurveyID', 'timestamp' => 'MIN(timestamp)'))
    ->where('status = ?', UserSurveyStatus::ACCESSED)
    ->group('userSurveyID');


$select = $db->select()
    // $selectColNames contains columns both from the main query and 
    // the subquery (e.g. firstAccess.timestamp AS dateFirstAccess).
    ->from(array('us' => 'user_surveys'), $selectColNames)
    ->joinLeft(array('firstAccess' => $subSelect), 'us.userSurveyID = firstAccess.userSurveyID', array())
    ->where('us.surveyID = ?', $surveyID);

这将导致以下MySQL查询：

SELECT `us`.`userSurveyID`, 
    // More columns from main query `us`
    `firstAccess`.`timestamp` AS `dateFirstAccess`
FROM `user_surveys` AS `us`
LEFT JOIN (
    SELECT `user_survey_status_entries`.`userSurveyID`, 
            MIN(timestamp) AS `timestamp` 
    FROM `user_survey_status_entries` 
    WHERE (status = 20) 
    GROUP BY `userSurveyID`
) AS `firstAccess` ON us.userSurveyID = firstAccess.userSurveyID 
WHERE (us.surveyID = '10')

我无法弄清楚如何使用教义2.5查询生成器加入子查询。在主查询中，我需要从子查询中选择列。

我在这里已经读到，该学说不支持加入子查询。如果仍然如此，是否可以使用主义DBAL的SQL查询构建器以其他方式编写此查询？原生SQL对我来说可能不是一个好的解决方案，因为此查询将在代码后面动态扩展。

Answer 1

通过将DQL示例改编为DBAL，我找到了解决方案。诀窍是获取子查询的原始SQL，将其包装在方括号中，然后将其联接。子查询中使用的参数必须在主查询中设置：

$subSelect = $connection->createQueryBuilder()
    ->select(array('userSurveyID', 'MIN(timestamp) timestamp'))
    ->from('user_survey_status_entries')
    // Instead of setting the parameter in the main query below, it could be quoted here:
    // ->where('status = ' . $connection->quote(UserSurveyStatus::ACCESSED))
    ->where('status = :status')
    ->groupBy('userSurveyID');

$select = $connection->createQueryBuilder()
    ->select($selectColNames)
    ->from('user_surveys', 'us')
    // Get raw subquery SQL and wrap in brackets.
    ->leftJoin('us', sprintf('(%s)', $subSelect->getSQL()), 'firstAccess', 'us.userSurveyID = firstAccess.userSurveyID')
    // Parameter used in subquery must be set in main query.
    ->setParameter('status', UserSurveyStatus::ACCESSED)
    ->where('us.surveyID = :surveyID')->setParameter('surveyID', $surveyID);