Izpuskash edna vazmojnost edna tablitsa da ya izpolzvash niakolko puti vuv FROM

SELECT
u1.userid, u2.userid
FROM
userinfo u1, userinfo u2, categories c, definitions d
WHERE
u1.categoryid=c.categoryid AND
d.userid=u2.userid AND
d.categoryid=u1.categoryid

tova e samo hint, dovarshi si ideata sam - krayniyat variant sigurno shte izglejda malko po-dulug s OR-ove i AND-ove