NHibernate HQL子查询问题
我的（简化的）域模型包含称为客户和产品之间的所有权的多对多关系。我想编写一个 NHibernate HQL 查询来统计拥有每种产品的客户数量（在特定条件下）。请注意，客户可以多次拥有给定产品，但这只能算作对该产品的一次“投票”。
执行此操作的 SQL 非常简单：
select ProductID, count(*)
from (
select distinct CustomerID, ProductID
from Ownership
where ...
) tbl
group by ProductID
不幸的是，HQL 不支持 from 子句中的子查询。如何用 HQL 表达这个查询？
My (simplified) domain model contains a many-to-many relationship called Ownership between Customer and Product. I would like to write an NHibernate HQL query that tallies the number of customers who own each product (under certain criteria). Note that a customer can own a given product multiple times, but this should only count as one "vote" for that product.
The SQL for this is easy enough:
select ProductID, count(*)
from (
select distinct CustomerID, ProductID
from Ownership
where ...
) tbl
group by ProductID
Unfortunately, HQL does not support subqueries in the from clause. How can I express this query in HQL?
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感谢贾森·麦克利
Credit to Jason Meckley