查詢加入問題

Question

爲什麼此查詢從兩個表而不是僅從OVPM返回？

SELECT * 
from OVPM M1 
JOIN VPM2 M2 ON M2.DocNum = M1.DocNum 
AND Canceled = 'N' 
WHERE M1.DocNum = '2292' 

Answer 1

因爲您查詢了所有內容*。如果你只需要OVPM的數據 - 用M1.*