How to create a query with Union using Nhibernate

Question

I need to implement a query in nhibernate make a union between 2 tables. In sql, it would be something like that:

SELECT T1.Id AS ID
FROM TABELA1 AS T1
UNION    
SELECT T2.Id AS ID
FROM TABELA2 AS T2

I couldn’t find any way to make one union, nor with QueryOver, nor with Linq.

Someone knows something that can help me?

Edit 1

With Linq I even came up with an "almost" solution, but an error occurred saying that Union is not supported by nhibernate. What I did was this:

var query = (from t1 in Session.Query<Tabela1>()
             select t1.Id
             ).Union(from t2 in Session.Query<Tabela2>()
                     select t2.Id);
query.ToList();

The mistake was this:

The Unionresultoperator result Operator is not Current supported

I don’t even know which way to go now, maybe I’ll have to do both selects separated and the union in remembrance.

Answer 1

If you have control over the database, you could create a view in the database, which makes Union, and then map a class of yours to the view. This would solve the problem.

If it’s not that way, I guess I’m just doing it in memory.

According to that answer in the SOEN, it is possible to use the method Future to make two queries on the same call to the bank, which would be better than making two separate calls. Still, all results would be returned, without eliminating duplicates, which would have to be done in memory.

var resultSet1 = this.Session.CreateCriteria<A>().Future<A>();
var resultSet2 = this.Session.CreateCriteria<B>().Future<B>();

Unfortunately, according to this another SOEN response, cannot be used Future with LINQ, until version 3, so it seems that the only way at the moment is to use the above syntax.