Question

Is it possible to do a join between 2 tables that don’t have foreign keys?

Edit: Ok, I have been assured this is possible, but I’m not entirely sure how to do it yet.

Classes

public class Booking
{
    public virtual int Id { get; set; }
    public virtual Int32 bookingID { get; set; }
    public virtual Int32 bookingAdminID { get; set; 
}

public class BookingLocation
{
    public virtual int Id { get; set; }
    public virtual Int32 bookingID { get; set; }
    public virtual Int32 locationID { get; set; } 
}

Mappings

 public BookingMap()
 {
    Table("Bookings");

    Id(x => x.Id).Column("ID");
    Map(x => x.bookingID).Column("BookingID");
    Map(x => x.bookingAdminID).Column("BookingAdminID");
 }

public class BookingLocation
{
    public virtual int Id { get; set; }
    public virtual Int32 bookingID { get; set; }
    public virtual Int32 locationID { get; set; } 
 }

I need to do a simple inner join on bookingID of both table above. How would I do that?

I have tried:

var hql = "select b from Booking as b inner join BookingLocation as bl on b.bookingID =   bl.bookingID";
var bookings = session.CreateQuery(hql).List<object[]>(); 

but I get the error:

Semantic exception was unhandled by user code Path expected for join!

[select b from Booking as b inner join BookingLocation as bl on
b.bookingID = bl.bookingID]

I am taking this approach because I can’t easily build a relationship between these 2 tables in the mapping. Do you need to have a relationship in order to do a join?

Answer 1

I was able to resolve this by adding relationships to my entities like so:

 public class Booking
 {
     public virtual int Id { get; set; }
     public virtual Int32 bookingID { get; set; }
     public virtual Int32 bookingAdminID { get; set; }


     public virtual IList<BookingLocation> BookingLocations { get; set; }

     public Booking()
     {
         BookingLocations = new List<BookingLocation>();
     }
 }

public class BookingLocation
{
    public virtual int Id { get; set; }
    public virtual Int32 bookingID { get; set; }
    public virtual Int32 locationID { get; set; } 
    public virtual Booking Booking { get; set; }
}

Even though they don’t have foreign keys, I was then able to do a join like this:

var bookings = session.CreateCriteria<Booking>("p")
                              .CreateCriteria("p.BookingLocations", JoinType.InnerJoin)
                              .SetMaxResults(30) 
                              .List<Booking>();