Question

真的很遗憾地向所有专家询问我对此SQL语句的错误。

我要做的就是从SalesExec表中列出销售人员，并显示新表中新车的数量以及该销售人员已售出的旧表中二手车的数量。

SELECT SALESEXEC.SALESEXECNAME 
COUNT(NewSALES.CHASSIS) AS newCOUNT
COUNT(UsedSales.CHASSIS) AS usedCOUNT
FROM SALESEXEC.csv SALESEXEC, NewSALES.csv NewSALES, UsedSALES.csv UsedSALES
WHERE SALESEXEC.ID = NewSALES.SALESEXECID And SALESEXEC.ID = UsedSALES.SALESEXECID
GROUP BY SALESEXEC.SALESEXECNAME

对于newCOUNT和usedCOUNT，此声明似乎返回相同的数字，我甚至不知道该数字来自何处？

同样，我真的很感激任何帮助。提前谢谢

史蒂夫

Answer 1

SELECT SALESEXEC.SALESEXECNAME, newCOUNT, usedCOUNT
FROM SALESEXEC.csv SALESEXEC
JOIN (
    SELECT SALESEXECID, COUNT(CHASSIS) AS newCOUNT
    FROM NewSALES.csv
    GROUP BY SALESEXECID
) NewSALES ON SALESEXEC.ID = NewSALES.SALESEXECID
JOIN (
    SELECT SALESEXECID, COUNT(CHASSIS) AS usedCOUNT
    FROM UsedSALES.csv 
    GROUP BY SALESEXECID
) UsedSALES ON SALESEXEC.ID = UsedSALES.SALESEXECID

另一个带有SQL语句的简单查询（来自某人刚刚学习SQL）

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