AI-NeuralNet-Simple-0.03 $ aiprolog mytables.pro 

Welcome to AI::Prolog v 0.732
Copyright (c) 2005, Curtis "Ovid" Poe.
AI::Prolog comes with ABSOLUTELY NO WARRANTY.  This library is free software;
you can redistribute it and/or modify it under the same terms as Perl itself.

Type '?' for help.

?- listing.

1. city_usr/3: 
   city_usr(A, B, C) :- 
        city(A, D),
        usr(D, B, C).
2. usr/3: 
   usr(1, John, 1).
   usr(1, Marry, 2).
   usr(2, Eva, 3).
   usr(3, Zby, 4).
3. city/2: 
   city('New York', 1).
   city(London, 2).
   city(Warsaw, 3).

listing 

Yes
?- city_usr('New York', User, ID).

city_usr('New York', John, 1) ;

city_usr('New York', Marry, 2) ;

 No
?-