Add support for joining a subquery in hql

src/NHibernate.DomainModel/Northwind/Entities/CompositeOrder.cs

@@ -0,0 +1,46 @@
+using System;
+
+namespace NHibernate.DomainModel.Northwind.Entities
+{
+	public class CompositeOrder : IEquatable<CompositeOrder>
+	{
+		public virtual int OrderId { get; set; }
+
+		public virtual Customer Customer { get; set; }
+
+		public virtual DateTime? OrderDate { get; set; }
+
+		public virtual DateTime? RequiredDate { get; set; }
+
+		public virtual DateTime? ShippingDate { get; set; }
+
+		public virtual Shipper Shipper { get; set; }
+
+		public virtual decimal? Freight { get; set; }
+
+		public virtual string ShippedTo { get; set; }
+
+		public override bool Equals(object obj)
+		{
+			if (ReferenceEquals(null, obj)) return false;
+			if (ReferenceEquals(this, obj)) return true;
+			if (obj.GetType() != GetType()) return false;
+			return Equals((CompositeOrder) obj);
+		}
+
+		public virtual bool Equals(CompositeOrder other)
+		{
+			if (ReferenceEquals(null, other)) return false;
+			if (ReferenceEquals(this, other)) return true;
+			return OrderId == other.OrderId && Equals(Customer, other.Customer);
+		}
+
+		public override int GetHashCode()
+		{
+			unchecked
+			{
+				return (OrderId * 397) ^ (Customer != null ? Customer.GetHashCode() : 0);
+			}
+		}
+	}
+}

src/NHibernate.DomainModel/Northwind/Entities/Northwind.cs

@@ -33,7 +33,12 @@ public IQueryable<Order> Orders
         {
             get { return _session.Query<Order>(); }
         }
-
+
+        public IQueryable<CompositeOrder> CompositeOrders
+        {
+            get { return _session.Query<CompositeOrder>(); }
+        }
+
         public IQueryable<OrderLine> OrderLines
         {
             get { return _session.Query<OrderLine>(); }

src/NHibernate.DomainModel/Northwind/Entities/Order.cs

@@ -90,6 +90,8 @@ public virtual ISet<OrderLine> OrderLines
             get { return _orderLines; }
         }
 
+        public virtual ISet<int> ProductIds { get; set; }
+
         public virtual void AddOrderLine(OrderLine orderLine)
         {
             if (!_orderLines.Contains(orderLine))

src/NHibernate.DomainModel/Northwind/Mappings/CompositeOrder.hbm.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="NHibernate.DomainModel.Northwind.Entities" assembly="NHibernate.DomainModel">
+  <class name="CompositeOrder" mutable="false" schema-action="none">
+    <subselect>
+      select * from Orders
+    </subselect>
+
+    <composite-id unsaved-value="any">
+      <key-property name="OrderId" column="OrderId" />
+      <key-many-to-one name="Customer" column="CustomerId" />
+    </composite-id>
+
+    <property name="OrderDate" column="OrderDate" />
+    <property name="RequiredDate" column="RequiredDate" />
+    <property name="ShippingDate" column="ShippedDate" />
+    <many-to-one name="Shipper" column="ShipVia" fetch="select"/>
+    <property name="Freight" column="Freight" />
+    <property name="ShippedTo" column="ShipName" type="string" length="40" />
+
+  </class>
+</hibernate-mapping>

src/NHibernate.DomainModel/Northwind/Mappings/Order.hbm.xml

@@ -60,6 +60,11 @@
 			<key column="OrderId"/>
 			<one-to-many class="OrderLine"/>
 		</set>
+
+    <set name="ProductIds" table="OrderLines">
+      <key column="OrderId" />
+      <element column="ProductId" type="Int32" />
+    </set>
 
 	</class>