sqlmax和Double-Join

我有以下三个表格：

student
-------
stnumb
stname
gender
grade
born

subject
-------
subjnumb
subjname
tname

results
-------
stnumb
subjnumb
percent

我需要返回每个学生的最高成绩及其科目

示例：鲍勃·史密斯，IPT，92岁

我得到的两个最接近的结果是：

SELECT  stname
    ,   subjname
    ,   highestmark
FROM    (
            SELECT      MAX(results.percent) as "highestmark"
                    ,   student.stname
                    ,   subject.subjname
            FROM        student
                    ,   subject
                    ,   results
            WHERE       results.stnumb      = student.stnumb
            AND         results.subjnumb    = subject.subjnumb
            GROUP BY    stname
        ) maxresult

……还有

SELECT      student.stname as Student
        ,   subject.subjname as Subject
        ,   results.percent as Mark
FROM        results 
JOIN        student
ON          results.stnumb = student.stnumb
JOIN        subject
ON          results.subjnumb = subject.subjnumb
ORDER BY    stname

有人能给我指一下正确的方向吗？我已经为此工作了好几天，没有任何进展。

从GROUP by中缺少SubName判断，这是MySql。MySql没有分析功能，所以您需要调用Top1的旧形式。有一个版本的派生表包含最大值。此表用于筛选原始表：

SELECT pct, subjname, stname 
FROM
(SELECT r.pct, sub.subjname, std.stname,
RANK () OVER (PARTITION BY sub.subjname ORDER BY r.pct) as rk
FROM student std 
INNER JOIN results r ON r.stnumb = std.stnumb 
INNER JOIN subject sub ON sub.subjnumb = r.subjnumb 
GROUP BY sub.subjname, std.stname, r.pct ) a
WHERE rk = 1

SELECT      student.stname as Student
        ,   subject.subjname as Subject
        ,   results.percent as Mark
FROM        results 
JOIN        student
ON          results.stnumb = student.stnumb
JOIN        subject
ON          results.subjnumb = subject.subjnumb
JOIN
(
   SELECT stnumb, MAX(percent) percent
     FROM results
    GROUP BY stnumb
) top1GradePerStudent
  ON results.stnumb = top1GradePerStudent.stnumb
 AND results.percent = top1GradePerStudent.percent
ORDER BY    stname

也不存在只检索百分比不高的学生记录的方法：

SELECT      student.stname as Student
        ,   subject.subjname as Subject
        ,   results.percent as Mark
FROM        results 
JOIN        student
ON          results.stnumb = student.stnumb
JOIN        subject
ON          results.subjnumb = subject.subjnumb
WHERE       NOT EXISTS 
            (
                SELECT null
                  FROM results r2
                 WHERE r2.stnumb = results.stnumb
                   AND r2.percent > results.percent
            )
ORDER BY    stname

这两种方式都会带来回报。如果每个学生都必须有一个记录，请用MAX或MIN括起subjectname，因为行中的所有其他数据都是相同的，所以选择哪个科目并不重要

---

另外，我没有测试这个问题。可能有输入错误，但基本方法是正确的。

它不起作用是非常模糊的，您具体有什么问题？我已经在sqlfiddle中测试了该查询并执行了它。虽然除了您提供的数据结构之外，我对您的数据结构一无所知，但我无法假设什么会“起作用”。我建议的方法是按…顺序排列而不是按…划分。。是解决您概述的问题的正确方法。我知道，这是含糊不清的，但我无法给出任何原因，当您输入错误的查询时，它所做的一切都不会返回任何内容，因此问题可能存在于任何地方。如果我知道更多，我会这么说。伙计，你是传奇人物！非常感谢！！！第一个查询工作得绝对完美。谢谢你的帮助。