; load from database
(defn get-activities [db users_id & [limit]]
  (let [query (if limit ["select * from activity where users_id = ? order by for_date desc limit ?" users_id limit]
                        ["select * from activity where users_id = ? order by for_date desc" users_id])]
    (j/query db query {:identifiers #(.replace % \_ \-)})))


; write to database
(s/fdef insert-activity :args (s/cat :db any? :content ::content :date inst? :users_id number?))
(defn insert-activity [db content date users_id]
  (j/insert! db :activity {:content  content
                           :for_date (new java.sql.Date (.getTime date))
                           :users_id users_id}))

; calling function
(db-act/insert-activity db "some text" (t-coerce/to-date (t-core/today)) 1)

; loading function
(db-act/get-activities db 1)

; ==> output:
:for-date #inst "2016-12-20T23:00:00.000-00:00"

; while as today clearly is the 21. of Dec here in Germany