如何用3個內連接獲得最大值？

代碼：

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;

只需要獲得甲級最高值，因此產量將下降縮短1行。

來源

2017-04-13 Nish Patel

您可以使用'SELECT MAX（年級）FROM ...' –

@Nish Patel您只想要最大值，或者您想要完整的詳細信息，哪個學生獲得最高等級和主題詳細信息？ –

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

你應該使用group by和max喜歡：

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

這會給你的學生名單和最大等級爲每個學生。

來源

2017-04-13 07:16:50

如何用3個內連接獲得最大值？

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