Question

这是我的疑问：

SELECT Cottage15.CNUM,Cottage15.Rent,Assignment15.Hours
FROM Cottage15
INNER JOIN Assignment15
ON Cottage15.CNUM=Assignment15.CNUM
ORDER BY Assignment15.AID;

它有效，但我无法弄清楚如何将Max功能应用于hours？我希望MAX(Assignment15.Hours)能起作用！？

此查询显示所有行，但我只希望它显示基于小时字段的数字最高的某些行。

Answer 1

我认为这就是你想要的

SELECT Cottage15.CNUM,Cottage15.Rent,Assignment15.Hours
FROM Cottage15
INNER JOIN Assignment15
ON Cottage15.CNUM=Assignment15.CNUM
WHERE Assignment15.Hours = (SELECT MAX(Assignment15.Hours) FROM Assignment15)
ORDER BY Assignment15.Hours

Answer 2

您必须添加组聚合才能应用Max函数

 SELECT Cottage15.CNUM,Cottage15.Rent,Max(Assignment15.Hours)
 FROM Cottage15
 INNER JOIN Assignment15
 ON Cottage15.CNUM=Assignment15.CNUM
 group by Cottage15.CNUM,Cottage15.Rent
 ORDER BY Assignment15.AID;

Answer 3

如果您希望每个max(hour)获得Cottage15.CNUM and Cottage15.Rent 然后使用max(Assignment15.Hours)和group by Cottage15.CNUM,Cottage15.Rent：

SELECT Cottage15.CNUM,Cottage15.Rent,MAX(Assignment15.Hours)
FROM Cottage15
INNER JOIN Assignment15
ON Cottage15.CNUM=Assignment15.CNUM
GROUP BY Cottage15.CNUM,Cottage15.Rent

但是如果你想让Cottage15.CNUM and Cottage15.Rent在整个结果集中有max(Assignment15.Hours)，那么你可以通过以下方式获得它：

SELECT Cottage15.CNUM,Cottage15.Rent,Assignment15.Hours
FROM Cottage15
INNER JOIN Assignment15
ON Cottage15.CNUM=Assignment15.CNUM
WHERE Assignment15.Hours = ( SELECT MAX(Assignment15.Hours)
                             FROM Cottage15
                             INNER JOIN Assignment15
                             ON Cottage15.CNUM=Assignment15.CNUM
                            )

如何在SQL中使用MAX函数？

3 个答案: