SELECT... WHERE.... OR... ??? Possible?

[admin]

I have a series of fields:

Cat1
SubCat1
Cat2
SubCat2
Cat3
SubCat3
etc. up to 5.

I want to SELECT from the database where $cat and $subcat match a pair above (but they must be the same number, not Cat1 and SubCat2 for example).

Before I added the extra cats, I had:

SELECT FROM sites WHERE Cat = '$cat' AND SubCat = '$subcat'

And I've tried loops and everything, but I'd really prefer to return them all in one go, because I run all sorts of stuff on the results and don't want to have to do it 5 times.

I've tried

SELECT FROM sites WHERE Cat1 = '$cat' AND SubCat1 = '$subcat' OR WHERE Cat2 = '$cat' AND SubCat2 = '$subcat'

but that doesn't seem to return anything at all.

Hope you can help, it's quite urgent, so I'd really appreciate any help.

Thanks in advance,

Danny