- Multiple (?) or order_by() in query condition

  Consider:

  #pragma ... query(foo.bar.not_null () && (?))

  If we substitute "ORDER BY ..." for (?), then we will get "... AND ORDER BY"
  in the statement. We can make it work by changing && to + but then if
  we actually have additional conditions, that won't work.

  One idea: have order_by() pragma? Though we can also have LIMIT, OFFSET,
  etc. This should also align with ORDER BY, etc syntax in general queries.

  Another idea: support multiple (?) that are "filled" from multiple
  query() arguments (C++11 variadic template).

- Member names for table views

  Currently we have to specify column names as strings in table views queries.
  There is no way to use view member names. If we support this, then is would
  also be useful to be able to add members that are not selected but can be
  used in query conditions (readonly?). Looks like we need a general way to
  describe a table (and generate query_columns from it).

  See email from frankiegp@libero.it/14-Jul-2014.

? std::duple-based view

  Can't we TMP-generate traits class in C++11? Could be useful for calling
  stored procedures, for example. Could also have specializations for common
  simple types (std::string, integers).