I've got a one to many association between a Carrier and Vehicle. In
my database my Vehicle table has a foreign key CarrierId.
The most efficient way to query vehicles by carrier would be:
select ... from Vehicles where Vehicles.CarrierId == 1
However, if I use QBC:
var fromDb = session.CreateCriteria<Vehicle>()
.CreateCriteria("Carrier",
global::NHibernate.SqlCommand.JoinType.InnerJoin)
.Add(Expression.Eq("Id", 1))
.AddOrder(new Order("BusinessRef", true))
.List<Vehicle>();
The result is:
NHibernate: SELECT this_.Id as Id1_1_, this_.VehicleType as
VehicleT2_1_1_, this_.BusinessRef as Business3_1_1_, this_.CarrierId
as CarrierId1_1_, carrier1_.Id as Id2_0_, carrier1_.Name as Name2_0_,
carrier1_.BusinessRef as Business3_2_0_ FROM Vehicles this_ inner join
Carriers carrier1_ on this_.CarrierId=carrier1_.Id WHERE carrier1_.Id
= @p0 ORDER BY carrier1_.BusinessRef asc;@p0 = 1
If I use NHibernate.Linq:
var fromDb2 = session.Linq<Vehicle>()
.Where(x => x.Carrier.Id == 1)
.OrderBy(x => x.BusinessRef)
.ToList();
The result is similar but always seems to do an outer join (how can I
force it to be left inner?):
NHibernate: SELECT this_.Id as Id1_1_, this_.VehicleType as
VehicleT2_1_1_, this_.BusinessRef as Business3_1_1_, this_.CarrierId
as CarrierId1_1_, carrier1_.Id as Id2_0_, carrier1_.Name as Name2_0_,
carrier1_.BusinessRef as Business3_2_0_ FROM Vehicles this_ left outer
join Carriers carrier1_ on this_.CarrierId=carrier1_.Id WHERE
carrier1_.Id = @p0 ORDER BY this_.BusinessRef asc;@p0 = 1
Finally if I use HQL (as much as I dislike using "magic" strings), the
result is exactly what I would expect and seems the most efficient:
var fromDb3 = session.CreateQuery("from Vehicle where
Carrier.Id = :id")
.SetParameter("id", 1)
.List<Vehicle>();
NHibernate: select vehicle0_.Id as Id1_, vehicle0_.VehicleType as
VehicleT2_1_, vehicle0_.BusinessRef as Business3_1_,
vehicle0_.CarrierId as CarrierId1_ from Vehicles vehicle0_ where
vehicle0_.carrier...@p0;@p0 = 1
So why do I get this difference and more importantly, how can I use
QBC or Linq to generate the same SQL as HQL does?
Thanks,
Ben
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