由于 几乎 总是，NHibernate的确实有这个答案。我们在这里想要实现的是这样的sql语句查找：
// final Request selection
SELECT request.[RequestId]
FROM [Request] request
// Only requests, which are successful, and have Max(date)
WHERE request.[RequestId] IN
(
SELECT successResponse.RequestId as y0_
FROM [Response] successResponse
// response which max date is equal to the upper response
// and which RequestId corresponds with supper upper Request
WHERE EXISTS
(
SELECT maxResponse.RequestId as y0_
, max(maxResponse.[DateTime]) as y1_
FROM [Response] maxResponse
// do the MAX only for current Request
WHERE maxResponse.RequestId = successResponse.RequestId
GROUP BY maxResponse.RequestId
// assure that the Response match is on the max DateTime
HAVING max(maxResponse.[DateTime]) = successResponse.[DateTime]
)
AND successResponse.[Success] = 1
)
笔记：
现在，NHibernate和QueryOver的神奇之处在于：
// This declaration will allow us, to use a reference from middle SELECT
// in the most deeper SELECT
Response response = null;
// the most INNER SELECT
var maxSubquery = QueryOver.Of<Response>()
.SelectList(l => l
.SelectGroup(item => item.RequestId)
.SelectMax(item => item.DateTime)
)
// WHERE Clause
.Where(item => item.RequestId == response.RequestId)
// HAVING Clause
.Where(Restrictions.EqProperty(
Projections.Max<Response>(item => item.DateTime),
Projections.Property(() => response.DateTime)
));
// the middle SELECT
var successSubquery = QueryOver.Of<Response>(() => response)
// to filter the Request
.Select(res => res.RequestId)
.WithSubquery
.WhereExists(maxSubquery)
// Now only these wich are successful
.Where(success => success.Success == true)
;
此时，我们必须嵌套内部SUB SELECT。让我们使用它们：
// the most outer SELECT
var query = session.QueryOver<Request>();
query.WithSubquery
// our Request ID is IN(...
.WhereProperty(r => r.ID)
.In(successSubquery);
var list = query
.List<Request>();
最后说明，我没有在讨论这个概念。没有表现。 我宁愿在响应“ IsActive”上使用一个设置，并使其更容易 …这仅仅是如何做到这一点的答案…
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