如何基于另一列的最大值获取一列的多个值？

Question

所以我有这张桌子

我想“打印”同一学期但其成绩最高不超过其学期最高成绩2分的人的姓氏。 例如，对于第4学期，所需的姓氏是“Παπαβασιλείου”（最高成绩= 9）和“Βαλκανιώτης”（成绩= 7> =（9-2））

我做的是这段代码，但不满足我的条件

SELECT GRADE as GRADE, SURNAME FROM pinakas2 
WHERE GRADE >= ((SELECT MAX(GRADE) FROM pinakas2) - 2) 
GROUP BY SEMESTER ORDER BY GRADE DESC

结果是：

Answer 1

删除GROUP BY ，而是改为按ORDER BY semester ：

SELECT GRADE as GRADE, SURNAME
FROM pinakas2 
WHERE GRADE >= ((SELECT MAX(GRADE) FROM pinakas2) - 2) 
ORDER BY SEMESTER, GRADE DESC

如果您希望每学期最高成绩减2，请执行相关子查询：

SELECT GRADE as GRADE, SURNAME
FROM pinakas2 p1
WHERE GRADE >= ((SELECT MAX(GRADE) FROM pinakas2 p2
                 where p1.semester = p2.semester) - 2) 
ORDER BY SEMESTER, GRADE DESC

Answer 2

首先，您需要一个子查询来找出本学期的最高成绩，如下所示：

        SELECT MAX(GRADE) GRADE, SEMESTER
          FROM pinakas2
         GROUP BY SEMESTER

然后，您需要使用它来检索所需的学生：

  SELECT a.GRADE, a.SURNAME, a.SEMESTER
    FROM pinakas2 a
    JOIN (
        SELECT MAX(GRADE) GRADE, SEMESTER
          FROM pinakas2
         GROUP BY SEMESTER
         ) b ON a.SEMESTER = b.SEMESTER AND a.GRADE >= b.GRADE - 2
   ORDER BY a.SURNAME, a.GRADE 

如果出于某种原因您不关心发生这种情况的学期，请改为这样做。

  SELECT DISTINCT a.GRADE, a.SURNAME
    FROM pinakas2 a
    JOIN (
        SELECT MAX(GRADE) GRADE, SEMESTER
          FROM pinakas2
         GROUP BY SEMESTER
         ) b ON a.SEMESTER = b.SEMESTER AND a.GRADE >= b.GRADE - 2
   ORDER BY a.SURNAME, a.GRADE