NHibernate query over comparing two sub queries - nhibernate

Question

How do you I combine two sub queries with queryover with WithSubQuery ? I want something like below (exact syntax doesn't matter):
query.WithSubquery.WhereValue(QueryOver.Of<Child>()
.Where(m => m.Parent.Id == paretAlias.Id)
.Select(Projections.Max("SomeProp")))
.Lt(QueryOver.Of<Child>(() => childAlias)
.Where(m => childAlias.Id == parentAlias.Id)
.Select(Projections.Max("SomeOtherProp")));
I can't see any methods of WithSubquery that allows me to compare two methods. It has
Where : takes a lambda
WhereProperty : takes a property compares with a sub query
WhereValue : takes a value compares with a sub query
WhereExists : takes a query.
Basically I want a method with that takes sub query and compares with another sub query
A sample output query in the sql would be :
select * from Parent inner join child on parent.id = child.parentid where
(select max(SomeProp) from child where child.parentid = parent.id) > (select max(SomeOtherProp) from child where child.parentid = parent.id)

Answer 1

I think you should be able to resolve your problem by slightly modifying the sql-query:
SELECT p.* FROM [Parent] as p
WHERE EXISTS
(
SELECT c.[parentId] as parentid FROM [Child] as c
WHERE c.[parentid] = p.[id]
GROUP BY c.[parentid]
HAVING MAX(c.[someProp]) < MAX(c.[someOtherProp])
)
If this returns the correct result set then you can implement it with QueryOver like so:
Parent p = null;
Child c = null;
var subquery = QueryOver.Of(() => c)
.SelectList(list => list.SelectGroup(() => c.ParentId))
.Where(Restrictions.LtProperty(
Projections.Max(() => c.SomeProp),
Projections.Max(() => c.SomeOtherProp)))
.And(Restrictions.EqProperty(
Projections.Property(() => c.ParentId),
Projections.Property(() => p.Id)));
var query = QueryOver.Of(() => p)
.WithSubquery.WhereExists(subquery);
IList<Parent> resutl = Session.CreateQuery(query);
I've already replied on a similar question, there is also a Criteria API version of the above query:
Selecting on Sub Queries in NHibernate with Critieria API
I hope this helps, cheers!