Question

从3个不同的主题中找到一个ID的最大值（标记），类似地为第二个ID等等。

表名-学生

+---------+---------+-------+
| stud_id | Subj    | Marks |
+---------+---------+-------+
| 1       | ENGLISH | 60    |
+---------+---------+-------+
| 1       | MATHS   | 50    |
+---------+---------+-------+
| 1       | HINDI   | 65    |
+---------+---------+-------+
| 2       | ENGLISH | 70    |
+---------+---------+-------+
| 2       | MATHS   | 20    |
+---------+---------+-------+
| 2       | HINDI   | 57    |
+---------+---------+-------+
| 3       | ENGLISH | 72    |
+---------+---------+-------+
| 3       | MATHS   | 88    |
+---------+---------+-------+
| 3       | HINDI   | 62    |
+---------+---------+-------+

结果应为：

+---------+---------+-------+
| stud_id | Subj    | Marks |
+---------+---------+-------+
| 1       | HINDI   | 65    |
+---------+---------+-------+
| 2       | ENGLISH | 70    |
+---------+---------+-------+
| 3       | MATHS   | 88    |
+---------+---------+-------+

查询：

SELECT STUD_ID, SUBJ, MAX(MARKS) marks FROM STUDENT group by id;

Answer 1

在相等的情况下，我同时拥有两个ID。

如果不是这种情况，请删除GROUP BY并将GROUP_CONCAT()替换为DISTINCT s1.Subj

SELECT GROUP_CONCAT(DISTINCT s1.stud_id
                    ORDER BY s1.stud_id ASC SEPARATOR ', '),
       s1.Subj,
       s1.Marks
FROM Student s1
   LEFT JOIN Student s2 ON s1.Marks < s2.Marks
     AND s1.Subj = s2.Subj
WHERE s2.stud_id IS NULL
GROUP BY s1.Subj

您可以测试Here

对于LEFT JOIN，实际具有最大值的行将在右侧具有NULL。然后，我过滤联接的结果，仅显示右侧为NULL的行。

从3个不同的主题中找到一个ID的最大值（标记），然后为第二个ID相似地搜索，依此类推

1 个答案: