在创建 CriteriaQuery 时需要帮助

Question

首先，我想知道是否可以这样做？

以下是我的查询，我正在尝试使用标准进行构建。

SELECT CONCAT('record-', rl.record_id) AS tempId, 
        'sloka' AS type, 
         rl.record_id AS recordId,
         rl.title AS title, 
         rl.locale as locale,
         rl.intro AS intro, 
         rl.title AS localetitle, 
         NULL AS audioUrl,
         lp.name AS byName,
         lp.person_id AS byId,
         lp.name AS onName,
         lp.person_id AS onId

    FROM record_locale rl 
        LEFT JOIN record r ON rl.record_id = r.record_id 
        LEFT JOIN locale_person lp ON r.written_on = lp.person_id 
    WHERE rl.title LIKE :title 
        AND rl.locale = :locale 
        AND lp.locale = :locale 

UNION 

SELECT CONCAT('lyric-', s.song_id) AS tempId, 
        'bhajan' AS type,
        s.song_id AS recordId,
        s.title, 
        l.locale as locale,
        NULL AS intro,
        l.title AS localetitle,
        s.audio_url AS audioUrl,
        lpb.name AS byName,
        lpb.person_id AS byId,
        lpo.name AS onName,
        lpo.person_id AS onId 

    FROM song s 
        LEFT JOIN locale_person lpb 
    ON (s.written_by = lpb.person_id AND lpb.locale = :locale) 
        LEFT JOIN locale_person lpo
    ON (s.written_on = lpo.person_id AND lpo.locale = lpb.locale)
        INNER JOIN lyric l 
    ON (l.locale = lpb.locale AND l.song_id = s.song_id) 

    WHERE s.title LIKE :title AND s.approved_by IS NOT NULL 

    ORDER BY localeTitle ASC

// END

根据少数情况，我可能需要两个查询的联合，或者只是没有联合的单个查询。

Answer 1

将 SQL 转换为 JPQL 通常是很好的第一步，因为我们无法完全确定这些表映射到什么，或者您期望返回什么。如果可以在 JPQL 中执行，则应该可以使用条件查询。除了在这种情况下：JPA/JPQL 没有联合运算符，因此它不能在直接的 JPA 中工作，但一些提供程序（如 EclipseLink）有支持。见：

UNION to JPA Query 和 http://www.eclipse.org/eclipselink/documentation/2.5/jpa/extensions/j_union.htm