Please Help With Complex Update Statement Logic

hi.

I am having probelms with an update statement. every time
i run it, "every" row updates, not just the one(s) intended.

so, here is what i have. i have tried this with both AND and OR
and neither seem to work.

i dont know why this is elluding me, but i'd appreciate help with the
solution.

thanks.

UPDATE add
SET add_s = 1
WHERE add.add_status = 0 and add.add_email = 'mags23@rice.edu'
or add_s in
(
SELECT a.add_s
FROM add a, edit e
WHERE a.email_address = e.email_address
and e.public_name = 'professor'
)