¿COMBINAR columnas de destino usando filas de origen?

WITH Pivoted AS
(
  SELECT person_ID, eye, hair, teeth
  FROM SourceBodyPartColors
    PIVOT
    (
    MAX (color) FOR body_part_name IN ( [eye], [hair], [teeth] )
    ) AS pvt
  )  
MERGE TargetBodyPartColors AS target
USING  Pivoted AS source
ON (target.person_ID = source.person_ID)
WHEN MATCHED THEN 
UPDATE SET eye_color = source.eye,  
           hair_color = source.hair,  
           teeth_color = source.teeth ;