Error1Dimension '...' : The following attribute(s) form loop(s):

Hello!

I have an error on a dimension, saying
"Error 1 Dimension 'Car Park Type' : The following attribute(s) form loop(s): [Car Park Type], [Car Park Key]. 0 0 "
but I do not have much idea of what it could mean.

This dimension is based on this request :
SELECT 'Inside' AS CarParkType, InsideCount AS CarParkCount, BuildingKey, OfferKey, TransactionKey, CarParkKey
FROM dimCarPark
WHERE (InsideCount > 0)
UNION
SELECT 'Outside' AS CarParkType, OutsideCount AS CarParkCount, BuildingKey, OfferKey, TransactionKey, CarParkKey + 100000 AS Expr1
FROM dimCarPark AS dimCarPark_3
WHERE (OutsideCount > 0)
UNION
SELECT 'Proximity' AS CarParkType, ProximityCount AS CarParkCount, BuildingKey, OfferKey, TransactionKey, CarParkKey + 200000 AS Expr1
FROM dimCarPark AS dimCarPark_2
WHERE (ProximityCount > 0)
UNION
SELECT 'Double' AS CarParkType, DoubleCount AS CarParkCount, BuildingKey, OfferKey, TransactionKey, CarParkKey + 300000 AS Expr1
FROM dimCarPark AS dimCarPark_1
WHERE (DoubleCount > 0)

Does anyone have any idea?

Thanks anyway.I have found. There was an error in the attributes of the dimension.

Bye!