ISOTOPE - Return Order ID from Unique ID

I have an ISOTOPE site for which I want to display the Order ID after a completed order.
After completition of the PayPal payment, PayPal returns to my site with UID=nnnnnnnnnnnnnnnnn in the URL and the order database is updated. The UID is a unique identifier which is recorded as a field in an order row, in the same row is the Order ID.

I am used to using PHP which allows inline SQL, with PHP I could just embed the following ....

SELECT order_id
FROM `tl_iso_orders`
WHERE `uniqid` = 'nnnnnnnnnnnnnnnnn'

and then echo the order_id to the page.

Can anybody tell me how can I do the same in Cantao?