Question

我有两个持久类Comment和Vote。 Comment可以与许多Vote相关联，并且它们之间存在@OneToMany - @ManyToOne关系，这些关系正常运行。我想要做的是按大多数赞成对评论进行排序。如果Vote列为Vote.up，则1为upvote;如果Vote.up为0，则select c from Comment c order by ( (select count(*) from c.votes v where v.up = 1) - (select count(*) from c.votes v where v.up = 0) ) desc为downvote。我试图找出他们的不同之处

到目前为止，这是我的HQL，但它无效

// resize the image
    switch (draggingResizer) {
      case 0:
        //top-left
        imageX = mouseX;
        imageWidth = imageRight - mouseX;
        imageY = mouseY;
        imageHeight = imageBottom - mouseY;
        break;
      case 1:
        //top-right
        imageY = mouseY;
        imageWidth = mouseX - imageX;
        imageHeight = imageWidth/ratio; //imageBottom - mouseY;
        break;
      case 2:
        //bottom-right
        imageWidth = mouseX - imageX;
        imageHeight = mouseY - imageY;
        break;
      case 3:
        //bottom-left
        imageX = mouseX;
        imageWidth = imageRight - mouseX;
        imageHeight = mouseY - imageY;
        break;
    }

有办法做到这一点吗？

Answer 1

HQL不支持这样的语法，因此您必须使用本机查询：

List<Comment> comments = (List<Comment>) session.createSQLQuery(
        "select * " +
        "from Comment " +
        "where id in (   " +
        "    select comment_id " +
        "    from (     " +
        "        select        " +
        "            c.id as comment_id,        " +
        "            SUM(CASE WHEN v.up=1 THEN 1 ELSE -1 END) AS vote_count     " +
        "        from Comment c     " +
        "        left join Votes v on c.id = v.comment_id     " +
        "        group by comment_id     " +
        "        order by vote_count desc   " +
        "    ) c_v " +
        ") c_id"
).addEntity(Comment.class).list();

Answer 2

看看这个SQL示例：

FROM Employee E WHERE E.id > 10 " +
         "ORDER BY E.firstName DESC, E.salary DESC

它是一个hql语句的例子。
你确定你的句子工作正常吗？

HQL按表达式排序

2 个答案: