Question

I am trying to create query which orders by child collection’s property. It is quite easy in SQL:

Select Table1.*
From Table1
Inner join Table2 on Table1.Id = Table2.Table1Id
OrderBy Table1.Column1, Table2.Column1

Here is how I did it in NHibernate 2 and it worked fine:

var result = Session.Linq<Table1>()
                 .OrderBy(x => x.Column1)
                     .ThenBy(x => x.Table2.FirstOrDefault().Column1);

After migrating to NHibernate 3 this doesn’t work anymore. It throws NHibernate.Hql.Ast.ANTLR.QuerySyntaxException: Antlr.Runtime.NoViableAltException.

I am using NHibernate 3.1. Are there other solutions for such query?

Answer 1

The two queries aren’t the same. The LINQ version (roughly) equates to:

SELECT Table1.*
FROM Table1
    INNER JOIN (SELECT TOP 1 * FROM Table2 WHERE Table2.Table1ID = Table1.Id) AS FirstTable2
ORDER BY Table1.Colum1, FirstTable2.Table2

EDIT

If you want to replicate the original sql you might want something like:

Session.Linq<Table1>()
    .SelectMany(t1 => t1.Table2, (t1,t2) => new { t1, t2 })
    .OrderBy(t1t2 => t1t2.t1.Column1)
    .ThenBy(t1t2 => t1t2.t2.Column2)
    .Select(t1t2 => t1)