As stated in the postmodern documentation, doquery allows you to execute the given query (a string or a list starting with a keyword), iterating over the rows in the result. The body will be executed with the values in the row bound to the symbols given in names. To iterate over a parameterised query, one can specify a list whose car is the query, and whose cdr contains the arguments.

The following is a toy function which illustrates the point.

(defun iterate-rows ()
  (let ((country-names ()))
    (doquery (:order-by (:select 'name 
                                 :from 'countries) 
                        'name) 
        (xname)
      (push xname country-names))
    country-names))