在JPA中获取查询交集? [英] Getting a query intersection in JPA?

问题描述

我有:"image" 1:许多"imageToTag"许多:1"tag"

I have: "image" 1:Many "imageToTag" Many:1 "tag"

我想发出一个查询，该查询将返回所有至少具有 标记[a，b，c]的图像.我不清楚如何在JPQL中对此建模.我可以动态地构建查询字符串，但这出于性能和安全性的考虑是不利的.有什么想法吗?

I want to issue a query that will return all images that have at least tags [a, b, c]. It's not clear to me how one can model this in JPQL. I could build the query string dynamically but that's bad for performance and security reasons. Any ideas?

推荐答案

在伪代码中:

SELECT * FROM IMAGES 
  INNER JOIN IMAGETAGS A
    ON IMAGE.ID = A.IMAGEID AND A.TAGID = 'A'
  INNER JOIN IMAGETAGS B
    ON IMAGE.ID = B.IMAGEID AND B.TAGID = 'B'
  INNER JOIN IMAGETAGS C
    ON IMAGE.ID = C.IMAGEID AND C.TAGID = 'C'

仅是猜测，但JPQL中的等效值将是

Just guessing, but the equivalent in JPQL would be

Select img from Image img 
 JOIN img.tag ta 
 JOIN img.tag tb 
 JOIN img.tag tc 
  WHERE ta.description = 'A' and tb.description = 'B' and tc.description = 'C'

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