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我想編寫JPA 2.1標準API這個SQL查詢:如何在內部查詢中引用外部查詢的成員?
select * from t_question q
where
(select count(*) from t_question_tag tag
where
q.question_id = tag.question_id
AND tag.tag_id in (18, 1)
) = 2;
我無法弄清楚如何引用外部問題成員內部查詢。
我目前在這一點上:
CriteriaQuery<Question> cq = criteriaBuilder.createQuery(Question.class);
Root<Question> questions = cq.from(Question.class);
cq.distinct(true);
Subquery<Long> selectTags = cq.subquery(Long.class);
Root<QuestionTag> qt = selectTags.from(QuestionTag.class);
Join<QuestionTag, Question> qtJoin = qt.join("question");
selectTags
.select(criteriaBuilder.count(qtJoin))
.where(
qt.get("tag").in(filter.getTags())
);
cq.where(criteriaBuilder.and(insArray),
criteriaBuilder.equal(criteriaBuilder.literal(filter.getTags().size()), selectTags));
但它創建了第二個加入。 SQL結果是:
SELECT DISTINCT ...
FROM T_QUESTION question0_
WHERE 1 =
(SELECT COUNT(question3_.question_id)
FROM T_QUESTION_TAG questionta2_
INNER JOIN T_QUESTION question3_
ON questionta2_.question_id=question3_.question_id
WHERE questionta2_.tag_id IN (18));
在你的第二個代碼片段中,'cq'代表什麼? (請相應更新代碼片段) – Riduidel
我並不確切知道JPA如何在這一點上工作,但似乎您的WHERE ... = 2成爲WHERE 1 = – Riduidel