NHibernate的QueryOver總結集合中的字段的值

Question

我有一個包含子項的集合父對象：

class Parent { 
    int Id {get;set;} 
    .... 
    IList<Child> Children {get;set;} 
} 

class Child { 
    int Id {get;set;} 
    int Value {get;set;} 
    ... 
    Parent Parent {get;set;} 
} 

蒙山FluentNHibernate的映射是

ParentMap：

Id(x => x.Id, "id").GeneratedBy.Assigned(); 
... 
HasMany<Child>(x => x.Children).AsBag().KeyColumn("parentid").Inverse() 
    .Fetch.Join().Cascade.AllDeleteOrphan(); 

ChildMap：

Id(x => x.Id).GeneratedBy.Assigned(); 
.... 
Map(x => x.Value, "value"); 
References<Parent>(x => x.Parent, "parentid").NotFound.Ignore(); 

我要地圖蒙山NHibernate的SQL查詢是這樣的：

select p.id, sum(c.value) 
from parent p, child c 
where p.id = c.parentid 

是否有可能把這種查詢蒙山QueryOver？

感謝

Answer 1

可以試一下這個

Child childAlias = null; 
var selection = session.QueryOver<Parent>() 
    .JoinAlias(p => p.Childs,() => childAlias) 
    .Select(Projections.Group(Projections.Id()), Projections.Sum(() => childAlias.Value)) 
    .List<object[]>() 
    .Select(arr => new { Id = (int)arr[0], Sum = (int)arr[1] }); 

或本

Child parentAlias = null; 
var selection = session.QueryOver(() => parentAlias) 
    .Select(Projections.Id(), Projections.SubQuery(QueryOver.Of<Child>() 
     .Where(c => c.Parent == parentAlias) 
     .Select(Projections.Sum<Child>(c => c.Value)) 
    .List<object[]>() 
    .Select(arr => new { Id = (int)arr[0], Sum = (int)arr[1] }); 

或本

IList selection = from p in session.Query<Parent> 
        select new { p.Id, Sum = p.Childs.Sum(c => c.Value) };