Question

我有一个带有列名

的sql表A.

name, id1, id2, val1

和一个列名为

的表B.

id1, id2, key1, key2

这是我的SQL查询

SELECT
  v1.id1,
  v1.id2
FROM (
       SELECT
         A.id1,
         A.id2,
         min(val1) AS x
       FROM A
         JOIN B ON A.id1 = B.id1 AND A.id2 = B.id2
       GROUP BY A.id1, A.id2
     ) AS v1
WHERE v1.x > 10

使用DetachedCriteria我能够形成子查询

DetachedCriteria subCriteria = DetachedCriteria.forClass(A_model.class);
subCriteria.createAlias("b", "b_model");
subCriteria.setProjection(Projections.projectionList()
                            .add(Projections.groupProperty("id1"))
.add(Projections.groupProperty("id2"))
.add(Projections.min("val1"),"x");

但我在创建外部查询时遇到了困难。

任何建议如何为上述SQL创建条件？

感谢您的期待。

Answer 1

Hibernate目前不支持from子句中的子选择。但是，您可以使用HAVING子句以更简单，更有效的形式重写您的查询：

SELECT A.id1, A.id2,
FROM A JOIN B ON A.id1 = B.id1 AND A.id2 = B.id2
GROUP BY A.id1, A.id2
HAVING min(val1) > 10

上述查询可以轻松移植到HQL或Criteria。

Answer 2

考虑为您需要的数据创建视图：

create view A_B_BY_ID1_AND_ID2 as
select A.id1,
       A.id2,
       min( val1 ) as x
from A
join B on A.id1 = B.id1 and A.id2 = B.id2
group by A.id1,
         A.id2

然后创建一个DTO来表示这些数据：

@Entity(table="A_B_BY_ID1_AND_ID2")
@Data //are you on board with lombok?
public class ABById1AndId2 {
    @Column
    private int x;
    @Column
    private int id1;
    @Column
    private int id2;
}

然后像其他任何东西一样访问它：

session.createCriteria(ABById1AndId2.class).add(Restrictions.gt("x", 10)).list();

Answer 3

HQL和Criteria对象既不支持从Select中选择。这里的解决方案是命名查询。

@NamedNativeQueries({
    @NamedNativeQuery(
    name = "findV1",
    query = "SELECT
              v1.id1,
              v1.id2
            FROM (
                   SELECT
                     A.id1,
                     A.id2,
                     min(val1) AS x
                   FROM A
                     JOIN B ON A.id1 = B.id1 AND A.id2 = B.id2
                   GROUP BY A.id1, A.id2
                 ) AS v1
            WHERE v1.x > 10"
    )
})

子选择在休眠标准中

3 个答案: