code: public static WithinGroup<Long> denseRank(Expression<?>... args) {
          return new WithinGroup<Long>(Long.class, SQLOps.DENSERANK2, args);
      }
docs: As an aggregate function, DENSE_RANK calculates the dense rank of a hypothetical row identified
  by the arguments of the function with respect to a given sort specification. The arguments of
  the function must all evaluate to constant expressions within each aggregate group, because they
  identify a single row within each group. The constant argument expressions and the expressions
  in the order_by_clause of the aggregate match by position. Therefore, the number of arguments
  must be the same and types must be compatible.
  
  @param args arguments
  @return dense_rank(args)