hql rank function, select in select causes antlr exception

I'm trying to make the following hql query work, but with no success. I'm trying to find out what rank has a specific user, dependent on a field value in a form. In SQL this works great.

SELECT tmp.rang
   开发者_运维百科 FROM (
          SELECT    b.ID as user, rank() as rang OVER (ORDER BY frh.Wert) 

          FROM      EKB.KennzahlenManagement.FormularResultHistorie as frh
          JOIN      frh.Formular_Bogen_K_Feld  fbkFeld
          JOIN      frh.Formular_Gesendent.Benutzer b

          WHERE     fbkFeld.FormularBogen.ID =:formularBogenId
          AND       fbkFeld.ResultFlag = 1
          AND       frh.Formular_Gesendent.Eingabe_nummer IN 
                                        (SELECT MAX(tmp.Eingabe_nummer) 
                                         FROM EKB.KennzahlenManagement.Formular_gesendet tmp
                                         WHERE tmp.Benutzer.ID = frh.Formular_Gesendent.Benutzer.ID 
                                         AND tmp.Formular.ID = frh.Formular_Gesendent.Formular.ID
                                         GROUP BY tmp.Benutzer
                                        )
    ) as tmp
    WHERE   tmp.usr =:userId 

So far I have identified two problems.

1) I get "NHibernate.Hql.Ast.ANTLR.QuerySyntaxException: Exception of type 'Antlr.Runtime.NoViableAltException' was thrown. near line..." because of the second select. How can I solve this problem? Any workarounds?

2) There seems to be something wrong with the rank() function. I'm also getting a similar exception like the one above. Is there no rank() in HQL? If there is, can you please give an example?

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As far as I know, RANK() is not currently implemented in NHibernate. You might want to try registering it as a custom function in the dialect. Here's an example to get you started. Registering RANK will probably be more complex than the example because of its syntax.