如何根据另一列的最大值获取列的多个值？

Question

所以我有这张桌子

我想“打印”那些同一学期的学生的姓氏，但他们的成绩最低也是他们学期最高年级的2分。例如，对于第四学期，所需的姓氏是“Παπαβασιλείου”（最高等级= 9）和“Βαλκανιώτης”（等级= 7> =（9-2））

我所做的就是这段代码，但它不符合我的标准

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，改为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分数减去2，请改为执行相关的子查询：

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查找本学期的最高成绩，如下所示：

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

然后你需要用它来检索你想要的学生：

  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 

如果由于某种原因您不关心发生这种情况的学期，请改为执行此操作。

  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