query.sql

SELECT Tax
FROM (
	SELECT Bookings.Tax AS Tax
	FROM Bookings 
	JOIN Field 
	ON Bookings.Code = Field.Code
	WHERE Field.IsCovered = 0
	GROUP BY Tax
	HAVING COUNT(Tax) >= 2
)
WHERE Tax NOT IN (
	SELECT DISTINCT Bookings.Tax AS Tax
	FROM Bookings
	JOIN Field
	ON Bookings.Code = Field.Code
	WHERE Field.IsCovered = 1
)