LOCAL i As Integer, n As Integer
CLOSE DATABASES ALL
*!* Create and populate the hash tables
CREATE CURSOR people_ids(id I, used L DEFAULT .F.)
INDEX ON id TAG id COLLATE "Machine"
INDEX ON used TAG used BINARY COLLATE "Machine"
SET ORDER TO 0
CREATE CURSOR nem_ids(id I, used L DEFAULT .F.)
INDEX ON id TAG id COLLATE "Machine"
INDEX ON used TAG used BINARY COLLATE "Machine"
SET ORDER TO 0
n = 100
FOR i = 1 TO n
    INSERT INTO people_ids (id) VALUES (i)
    INSERT INTO nem_ids (id) VALUES (i)
ENDFOR	

CREATE CURSOR people (age I, name V(16), id I)
INDEX ON id TAG id COLLATE "Machine"
INDEX ON name TAG name COLLATE "Machine"
SET ORDER TO 0
INSERT INTO people (age, name) VALUES (27, "Jonah")
INSERT INTO people (age, name) VALUES (18, "Alan")
INSERT INTO people (age, name) VALUES (28, "Glory")
INSERT INTO people (age, name) VALUES (18, "Popeye")
INSERT INTO people (age, name) VALUES (28, "Alan")
REPLACE id WITH HashMe("people_ids") ALL

*!* The plural of nemesis is nemeses
CREATE CURSOR nemeses (name V(16), nemesis V(16), p_id I, id I)
INDEX ON id TAG id COLLATE "Machine"
INDEX ON p_id TAG p_id COLLATE "Machine"
INDEX ON name TAG name COLLATE "Machine"
SET ORDER TO 0

INSERT INTO nemeses (name, nemesis) VALUES ("Jonah", "Whales")
INSERT INTO nemeses (name, nemesis) VALUES ("Jonah", "Spiders")
INSERT INTO nemeses (name, nemesis) VALUES ("Alan", "Ghosts")
INSERT INTO nemeses (name, nemesis) VALUES ("Alan", "Zombies")
INSERT INTO nemeses (name, nemesis) VALUES ("Glory", "Buffy")
REPLACE id WITH HashMe("nem_ids") ALL
UPDATE nemeses SET p_id = people.id FROM people ;
WHERE nemeses.name = people.name

*!* Show the join
SELECT pe.age, pe.name, ne.nemesis FROM people pe ;
JOIN nemeses ne ON pe.id = ne.p_id TO FILE "hashjoin.txt"

FUNCTION HashMe(cTable As String) As Integer
LOCAL ARRAY a[1]
SELECT MIN(id) FROM (cTable) WHERE NOT used INTO ARRAY a
UPDATE (cTable) SET used = .T. WHERE id = a[1]
RETURN a[1]
ENDFUNC