Selecting fields from subqueries?

[Robert Berry]

Hiya, I hope this is the right place for this, not sure where to post it ... I'm self-taught in MySQL but can't seem to find an answer for this in the manual. I was wondering in a SELECT query whether you can also return in the results fields selected from Subqueries. So, my SQL so far is like this:

SELECT cart_to_attribute.*
FROM cart
LEFT JOIN cart_to_attribute
ON(cart.cart_id = cart_to_attribute.cart_id)
WHERE cart.sessionhash = '$sessionhash'
AND (cart_to_attribute.attribute_id, cart.product_id) =
ANY
(SELECT cart_to_attribute.attribute_id, cart.product_id
FROM cart
LEFT JOIN cart_to_attribute
ON(cart.cart_id = cart_to_attribute.cart_id)
WHERE cart.user_id = $cookie_userid)

So what I'd like to do is also get the cart_id from the subquery (which is selecting by cart.user_id) returned in the results. Can this be done via subqueries or would I have to rewrite it as some sort of join?

Thanks, and apologies if I'm not supposed to post this here.