mixster

SELECT newword.word FROM
words newword, [words wpreN,]
sentences newsent [,sentences spreN]
WHERE
[wpreN.word=%s AND]
[spreN.wid=wpreN.id AND
 spre(N-1).id=spreN.pid AND]
newsent.pid=spreN.id
AND newword.id=newsent.wid
ORDER BY RAND()
LIMIT 1;