isnull(列名,'无')没有显示“无”

SELECT ProductName+'-'+ISNULL(NULLIF(Priority, ''), '无值') FROM Doctor_Product_Priority WHERE DoctorCode='HCP011290'
UNION
SELECT ProductName+'-'+ISNULL(NULLIF(Priority, ''), '无值') FROM Doctor_Product_Priority WHERE SpeakerCode='KOL0002162'