Postgresql functions are typically inserted into s-sql in their own form prefaced with : and their parameters are generally single quoted. Here are a few simple examples.

:min

:max

:version

(query (:select (:version)))
(("PostgreSQL 9.2 on x86_64-pc-linux-gnu, compiled by GCC x86_64"))
:random

(query (:limit (:order-by (:select 'id 'name :from 'countries)
                          (:random))
        5))

((54 "Israel") (62 "South Africa") (195 "Aruba") (79 "Costa Rica")
(31 "OECD"))

:avg

(froundn (query (:select (:avg 'latitude)
                         :from 'countries)
                :single)
         4)

18.4209



(defun table-size (table-name)
  "Return the size of a postgresql table in k or m. Table-name can be either a
string or quoted."
  (when (symbolp table-name) 
    (setf table-name  (string-downcase (write-to-string table-name))))
  (query (:select (:pg_size_pretty (:pg_total_relation_size'$1)))
         :single
         table-name))



(table-size 'countries)

"88 kB"

(defun current-database-size-pretty ()
  "Returns the current database size as a string in MB"
  (query (:select (:pg_size_pretty
                   (:pg_database_size (:current_database))))
         :single))