如何用3个内连接获得最大值？

代码：

SELECT StudFirstName, StudLastName, sc.ClassID, sub.SubjectID, sub.CategoryID, Grade 
FROM SS_Students as st INNER JOIN SS_Student_Schedules as ss 
ON st.StudentID = ss.StudentID 
INNER JOIN SS_Classes as sc 
ON ss.ClassID = sc.ClassID 
INNER JOIN SS_Subjects as sub 
ON sc.SubjectID = sub.SubjectID;

只需要获得甲级最高值，因此产量将下降缩短1行。

来源

2017-04-13 Nish Patel

您可以使用'SELECT MAX（年级）FROM ...' –

@Nish Patel您只想要最大值，或者您想要完整的详细信息，哪个学生获得最高等级和主题详细信息？ –

ORDER BY grade DESC LIMIT 1;否则，请参阅https://meta.stackoverflow.com/questions/333952/why-should-i-provide-an-mcve-for-what-seems-to-me-to-be-a-very-simple-sql - 查询 – Strawberry

你应该使用group by和max喜欢：

SELECT StudFirstName, StudLastName, sc.ClassID, sub.SubjectID, sub.CategoryID, MAX(Grade) 
FROM SS_Students as st INNER JOIN SS_Student_Schedules as ss 
    ON st.StudentID = ss.StudentID 
INNER JOIN SS_Classes as sc 
    ON ss.ClassID = sc.ClassID 
INNER JOIN SS_Subjects as sub 
    ON sc.SubjectID = sub.SubjectID 
GROUP BY StudFirstName, StudLastName, sc.ClassID, sub.SubjectID, sub.CategoryID

这会给你的学生名单和最大等级为每个学生。

来源

2017-04-13 07:16:50

如何用3个内连接获得最大值？

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