我在Nhibernate QueryOver中有一个查询,它会带回一组剧集对象(剧集作为一种护理法术),而这些剧集又将一组剧集状态作为每集的属性。但是我想改变这一点,以便每一集只会带回该剧集的最新状态更新,而不是全部。
执行此操作的SQL如下:
SELECT *
FROM DIPEpisode e
INNER JOIN DIPEpisodeStatus s on s.EpisodeID = e.SequenceID
WHERE e.ClientID = '1000001'
AND s.SequenceID IN (
SELECT TOP 1 SequenceID
FROM DIPEpisodeStatus s
WHERE s.EpisodeID = e.SequenceID
ORDER BY StatusRecordedDate DESC
)
我写了以下查询,它几乎可以提供我需要的内容
var statuses =
QueryOver.Of<DIPEpisodeStatus>()
.OrderBy(x => x.StatusRecordedDate).Desc
.Select(x => x.Id).Take(1);
DIPEpisodeStatus statusAlias = null;
return
session.QueryOver<DIPEpisode>()
.JoinQueryOver(x => x.DIPEpisodeStatuss, () => statusAlias)
.Fetch(x => x.AgencyID).Eager
.Fetch(x => x.DIPEpisodeStatuss).Eager
.Where(e => e.ClientID.Id == this.clientId)
.WithSubquery.WhereProperty(x => x.Id).Eq(statuses)
.List();
这将生成以下SQL:
SELECT *
FROM DIPEpisode this_
inner join DIPEpisodeStatus statusalia1_
on this_.SequenceID = statusalia1_.EpisodeID
WHERE statusalia1_.ClientID = '1000001' /* @p0 */
and statusalia1_.SequenceID = (SELECT TOP (1 /* @p1 */) this_0_.SequenceID as y0_
FROM DIPEpisodeStatus this_0_
ORDER BY this_0_.StatusRecordedDate desc)
正如您所看到的,唯一缺少的是子查询中的where子句。我需要对查询进行哪些更改才能生成此额外的where子句并仅撤回最新的状态更新?
由于
本
答案 0 :(得分:3)
集合DIPEpisodeStatuss
始终使用所有实体进行初始化,否则会破坏更改跟踪。您可以为集合定义过滤器,也可以根据需要返回DTO。此外,fetch将被忽略,因为它无法在一个sql语句中加载和过滤。
NHibernate filters are explained here
如何使用DTO
// assuming SequneceID and StatusRecordedDate correlates
var subquery = QueryOver.Of<DIPEpisode>()
.Where(e => e.ClientID.Id == this.clientId)
.JoinAlias(e => e.DIPEpisodeStatuss, () => statusAlias)
.Select(Projections.Max(() => statusAlias.SequenceID));
// or as in question
var subquery = QueryOver.Of<DIPEpisode>()
.Where(e => e.ClientID.Id == this.clientId)
.JoinAlias(e => e.DIPEpisodeStatuss, () => statusAlias)
.OrderByDescending(() => statusAlias.StatusRecordedDate)
.Select(() => statusAlias.SequenceID)
.Take(1);
DIPEpisodeDto dto = null;
DIPEpisodeStatus statusAlias = null;
return session.QueryOver<DIPEpisode>()
.Where(e => e.ClientID.Id == this.clientId)
.JoinQueryOver(e => e.DIPEpisodeStatuss, () => statusAlias)
.WithSubquery.WhereProperty(estatus => estatus.Id).Eq(statuses)
.SelectList(list => list
.Select(e => e.Whatever).WithAlias(() => dto.Whatever)
.Select(() => statusAlias.SquenceId).WithAlias(() => dto.StatusId)
...
)
.TransFormUsing(Transformers.AliasToBean<DIPEpisodeDto>())
.List();
或使用LINQ
var query = from e in session.Query<DIPEpisode>()
from s in e.DIPEpisodeStatuss
where e.ClientID.Id == this.clientId
where s.Id == (
from e2 in session.Query<DIPEpisode>()
from s2 in e2.DIPEpisodeStatuss
orderby s2.StatusRecordedDate descending
select s2.Id)
.First()
select new DIPEpisodeDto
{
e.Prop1,
Status = s,
};
return query.List<DIPEpisodeDto>();