在 hql 中的分区上的 row_number()答案

【问题标题】：row_number() over partition in hql在 hql 中的分区上的 row_number()
【发布时间】：2014-05-11 18:20:07
【问题描述】：

hql 中分区上的 row_number() 等价物是什么我在 hql 中有以下查询：

select s.Companyname, p.Productname, sum(od.Unitprice * od.Quantity - od.Discount) as SalesAmount FROM OrderDetails as od inner join od.Orders as o inner join od.Products as p " +
                                                              "inner join p.Suppliers as s" +
                                                      " where o.Orderdate between '2010/01/01' and '2014/01/01' GROUP BY s.Companyname,p.Productname"

我想通过s.Companyname 进行分区，其中RowNumber <= n。

【问题讨论】：

标签： hql window-functions

【解决方案1】：

按分区的行号如下所示：

row_number() over (partition by s.Companyname)

你不能在where子句中使用窗口函数row_number，所以你必须用它的值过滤子查询：

select * from (
  -- here is your query
  select 
    ...,
    row_number() over (partition by s.Companyname) as rowNum
  from ...
  where ...
) as res
where rowNum <= n

【讨论】：

【解决方案2】：

据我所知，row_number() 既不能用于 HQL，也不能用于 JPQL。在这种情况下，我建议使用native SQL 查询：

@PersistenceContext
protected EntityManager entityManager;
...

    String sQuery = "SELECT q.* FROM (" +
            "SELECT s.company_name, " +
               "p.product_name, " +
               "sum(od.unit_price * od.quantity - od.discount) as SalesAmount, " +
               "row_number() OVER (partition by s.company_name) as rn " +
            "FROM OrderDetails od " +
            "INNER JOIN Orders o ON o.id = od.order_id " +
            "INNER JOIN Products p ON p.id = od.product_id " +
            "INNER JOIN Suppliers s ON s.id = p.supplier_id " +
            "WHERE o.order_date between '2010/01/01' and '2014/01/01') as q " +
        "WHERE rn <= :n";

    List<ResultDbo> results = new ArrayList<>();
    Query query = entityManager.createNativeQuery(sQuery);
    query.setParameter("n", n);
    List<Object[]> resultSet = query.getResultList();
    for (Object[] resultItem : resultSet) {
        ResultDbo result = new ResultDbo();
        result.setCompanyName((String) resultItem[0]);
        result.setProductName((String) resultItem[1]);
        result.setSalesAmount((String) resultItem[2]);
        results.add(result);
    }

如果您曾经尝试在 HQL 中使用 OVER()，您几乎肯定会遇到一些验证异常，例如 java.lang.IllegalArgumentException: org.hibernate.hql.internal.ast.QuerySyntaxException: unexpected token: OVER near line 1, column 42 ...

【讨论】：