How can I fetch entities that has not been saved into another table?

[wlandgraf (Wagner Landgraf)]

You can use Sql condition to add the condition part in raw SQL, as described in these Support Center topics:

Filtering data with two many valued associations

In this case you should use SQL expressions, using, for example, EXISTS clause. Pseudo-code: Find<TAnagrFiscale> .Where(Linq.Sql('Exists SELECT * FROM AnagrIndirizzo AI WHERE field like '%' and AI.Id = {ID}'))