sql - 如何正确join和query实现比较

Answer 1

尝试这个：

SELECT ItemCode,
       CASE WHEN artfilename IS NULL
       THEN 'NoArtwork'
       ELSE fileLocation
       END
FROM OITM
LEFT OUTER JOIN  artfileStatus ON OITM.ItemCode = SUBSTRING(artfileStatus.artfilename , 1, 6)