dynamic sql generation in clojure

sql.clj

(require '[cheshire.core :as json]
         '[clojure.string :as string]
         '[yesql.core :as yesql])

(defmulti ->sql "converts a given val to Postgres-compatible SQL" class)

(defmethod to->sql :default ([f] f))
(defmethod to->sql String (str "'" f "'"))
(defmethod to->sql org.joda.time.DateTime ([f] ((str "CAST('" f "' AS TIMESTAMP)")))
(defmethod to->sql clojure.lang.PersistentVector ([f] (str "ARRAY[" (string/join ", " f) "]")))
(defmethod to->sql clojure.lang.PersistentArrayMap ([f] (str "'" (json/encode f) "'")))

(defn build-create-query
  [tablename params]
  "ex: users, {:first_name 'Nancy' :last_name 'Drew'}
   -> 'INSERT INTO users (first_name, last_name)
       VALUES ('Nancy', 'Drew')'"
  (let [attrs  (string/join ", " (map (comp name first) params))
        values (string/join ", " (map (comp ->sql second) params))]
  (str "INSERT INTO " tablename " (" attrs ") "
       "VALUES (" values ") "
       "RETURNING *;")))

(defn build-update-query
  [tablename params id]
  "ex: users, {:first_name 'George' :last_name 'Fayne' :id 7}, :id
   -> 'UPDATE users
       SET first_name = 'George',
           last_name  = 'Fayne'
       WHERE id = 7
       RETURNING *;"
  (let [id-val (get params id)
        params (dissoc params id)
        val-pairs (string/join
                    ", "
                    (map
                      #(str (name (first %)) " = " (->sql (second %)))
                      params))]
  (str "UPDATE " tablename
       " SET " val-pairs
       " WHERE " (name id) " = " (->sql id-val)
       " RETURNING *;")))

(defn db-create!
  [tablename params]
  (let [query (build-create-query tablename params)]
    (first (yesql.generate/query-handler @pg-conn query {}))))
            
(defn db-update!
  [tablename params id]
  (let [query (build-update-query tablename params id)]
    (first (yesql.generate/query-handler @pg-conn query {}))))