Does it have a sence?

does the last two lines of the query have sense?

SELECT a.f1, a.f2, b.f1, b.f2FROM a, b
WHERE a.f1 = b.f1
AND a.f2 = b.f2
AND nvl(a.f2, '!') <> nvl(b.f2, '!')
Thanks,

P.S. It is not student work . Received on Mon Jan 31 2005 - 11:26:13 CST