Clojure-SQL relational algebra / query composition

clojure-sql-demo.clj

(ns clojure-sql-demo
   (:require [clojure-sql.core :as sql]) ;;[clojure-sql "0.2.0-SNAPSHOT"]

(def user-emails
  (-> (sql/table :user_email_history)
      (sql/project {:email :user_email_history.email
                    :user_id :user_email_history.user_id
                    :email_request_id :user_email_history.email_request_id})))

(def users
  (-> (sql/table :users)
      (sql/project {:user_id :users.user_id
                    :email_request_id :users.email_request_id})))

(def users-with-email
  (-> users
      (sql/join user-emails :on `(and (= :user_email_history.email_request_id :users.email_request_id)
                                      (= :user_email_history.user_id :users.user_id)))
      (sql/project {:users.user_id :user_id
                    :user_email_history.email :email})))

(defn users-by-email [email]
  (-> users-with-email
      (sql/select `(= :email ~email))))

;; (users-by-email "[email protected]") => 
;;
;; ["SELECT \"table20393\".\"email\" AS \"email\",
;;         \"users20330\".\"user_id\" AS \"user_id\" 
;;  FROM (\"users\" AS \"users20330\" INNER JOIN 
;;        \"user_email_history\" AS \"table20393\" 
;;            ON ((\"table20393\".\"email_request_id\" = \"users20330\".\"email_request_id\")
;;            AND (\"table20393\".\"user_id\" = \"users20330\".\"user_id\")))
;;  WHERE (\"table20393\".\"email\" = ?)"
;; 
;; "[email protected]"]