join-csvs.clj

(require '[clojure.data.csv :as csv]
         '[clojure.java.io :as io])


(defn open-csv [file]
 (with-open [in-file (io/reader file)]
   (doall
    (csv/read-csv in-file))))

(defn map-csv-row [fields file]
  (map (fn [row] (zipmap fields row)) 
       (open-csv file)))

(defn id-extract [col i]
  (merge col
         {(:id i) (merge i (get col (:id i)))}))

(defn add-csv
  [hm fields file]
  (reduce id-extract 
          hm 
          (map-csv-row fields file)))

(defn -main []
  (add-csv (add-csv {} [:id :first :middle :last] "input.csv")
           [:id :age :month] "input2.csv"))