MySQL数据透视表动态行

Question

我需要你的帮助。

我有一张如下表所示的表格;

+-------+-----------+-----------+-----+--------+-------------+ | grade | firstname | lastname | age | gender | student_num | +-------+-----------+-----------+-----+--------+-------------+ | 2 | Stephen | Harper | 12 | male | 1 | | 1 | Jennifer | Solomon | 10 | female | 1 | | 4 | James | Barney | 9 | female | 1 | | 3 | Collins | Balmer | 8 | female | 1 | | 4 | Kehinde | Adefemi | 12 | male | 2 | | 2 | Benjamin | Salem | 14 | female | 2 | | 3 | Praise | Olawale | 9 | male | 2 | | 1 | Janet | Pelumi | 7 | male | 2 | | 3 | Ire | Adora | 11 | female | 3 | | 2 | Manny | Grace | 13 | male | 3 | | 2 | Esther | Benson | 7 | female | 4 | | 3 | Stan | Collimore | 6 | female | 4 |

请帮助我使用SQL生成下面的结果表。

grade|s1_fname |s1_age|s1_gender|s2_fname |s2_age|s2_gender 1 | Jennifer | 10 |female | Janet | 7 | male | 2 | Stephen | 12 |male | Benjamin| 14 | female| 3 | Collins | 8 |female | Praise | 9 | male | 4 | Kehinde | 12 |male | Myedan | 8 | male |

其中s1表示student1。 1应该来自student_num专栏

其中s2表示student2。 2应该来自student_num列 ...

我的数据库服务器也是MySQL。

谢谢！

我了解到这样的表叫做PIVOT表。

我已尝试过以下代码

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
          'SUM(CASE WHEN `grade` = ',
          `grade`,
          ' THEN firstname ELSE 0 END) AS `s',
          `student_num`, '_fname`'
        )
    ) INTO @sql
FROM students;
SET @sql = CONCAT('SELECT grade, ', @sql, ' FROM students GROUP BY grade');
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

Answer 1

SELECT s1.grade, s1.firstname AS s1_fname, s1.age AS s1_age, s1.gender AS s1_gender, 
       s2.firstname AS s2_fname, s2.age AS s2_age, s2.gender AS s2_gender
FROM students s1 JOIN students s2 ON s1.student_num = 1 
     AND s2.student_num = 2 AND s1.grade = s2.grade
ORDER BY s1.grade;