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我挣扎理解为什么这两个说法都给予同样的输出的输出:无法理解涉及鲜明
案例1:
SELECT sum(DISTINCT prod_price)
FROM PRODUCTS
案例2:
SELECT SUM(SQ.COST)
FROM (SELECT DISTINCT [VEND_ID] as PROD,[PROD_PRICE] as COST FROM PRODUCTS) SQ
哪里我的输出为SELECT * FROM Products
看起来像:
+1,很好的解释。 – radar 2014-11-06 18:11:44
@RADAR谢谢:)很高兴能帮助别人理解。 – SMA 2014-11-07 11:38:45