Clojure workshop memory db

memorydb.clj

(def memory-db "A blank database" (atom {}))

(defn read-db "Return the entire database" [] @memory-db)
(defn write-db "Update the database" [new-db] (reset! memory-db new-db))

(defn create-table "Create a new table" [table] 
  (write-db (assoc-in (read-db) [table] {:data [], :indexes {}})))

(defn drop-table "Destroy a table" [table] 
  (write-db (dissoc (read-db) table)))

(defn insert "Insert a record in a table with the id-key as index" [table record id-key]
		(
  		if (get-in (read-db) [table :indexes id-key (record id-key)])
  		(println (str "ERROR: id '" (record id-key) "' already exists in " table))
			 (let [
			     database (read-db)
			  	  idx (count (get-in database [table :data]))
			  	  updated-db (assoc-in database [table :data] (conj (get-in database [table :data]) record))
			  	  updated-idx (assoc-in updated-db [table :indexes id-key (record id-key)] idx)
			   ] 
				  (write-db updated-idx)
		  )
		)
)

(defn select-* "Return every record in a table" [table]
  (get-in (read-db) [table :data])
)

(defn select-*-where "Return the record from table with the give id-key value" [table id-key value]  
  (let [
		    database (read-db)
		    idx (get-in database [table :indexes id-key value])
		  ]
    ((get-in database [table :data]) idx)
  )
)

;--------------------------------------------------------------------------------
(create-table :clients)
(create-table :fruits)
(create-table :purchases)
(insert :clients {:id 1 :name "Bob" :age 32} :id)
(insert :clients {:id 2 :name "Alice" :age 24} :id)
(insert :fruits {:name "Lemon" :stock 24} :name)
(insert :fruits {:name "Coconut" :stock 3} :name)
(insert :fruits {:name "Pear" :stock 3} :name)
(insert :purchases {:id 1 :user-id 1 :item "Coconut"} :id)
(insert :purchases {:id 2 :user-id 2 :item "Lemon"} :id)