Hash join: Difference between revisions

</pre>

=={{header|Clojure}}==

<lang clojure>

(defn hash-join [table1 col1 table2 col2]

(let [hashed (group-by col1 table1)]

(flatten

(for [r table2]

(for [s (hashed (col2 r))]

(merge s r))))))

</lang>

Sample run:

<lang clojure>

(def s '({:age 27 :name "Jonah"}

{:age 18 :name "Alan"}

{:age 28 :name "Glory"}

{:age 18 :name "Popeye"}

{:age 28 :name "Alan"}))

(def r '({:nemesis "Whales" :name "Jonah"}

{:nemesis "Spiders" :name "Jonah"}

{:nemesis "Ghosts" :name "Alan"}

{:nemesis "Zombies" :name "Alan"}

{:nemesis "Buffy" :name "Glory"}))

(pprint (sort-by :name (hash-join s :name r :name)))

</lang>

Produces:

<pre>

({:nemesis "Ghosts", :age 18, :name "Alan"}

{:nemesis "Ghosts", :age 28, :name "Alan"}

{:nemesis "Zombies", :age 18, :name "Alan"}

{:nemesis "Zombies", :age 28, :name "Alan"}

{:nemesis "Buffy", :age 28, :name "Glory"}

{:nemesis "Whales", :age 27, :name "Jonah"}

{:nemesis "Spiders", :age 27, :name "Jonah"})