Question

距离我上次发布已经有很长时间了（今天我头疼得要命），所以如果这个问题被解决，我会明白的。

我要联接多个表以获取如下所示的数据（https://meta.stackexchange.com/questions/73566/is-there-markdown-to-create-tables在StackOverflow上确实没有表视图吗？）

| course_name    | student_name  |  credit_type  | 
| course_1       | student_1     |  credit_2     |
| course_1       | student_1     |  credit_3     |
| course_1       | student_1     |  credit_4     |
| course_1       | student_2     |  credit_1     |
| course_1       | student_2     |  credit_2     |
| course_1       | student_2     |  credit_3     |
| course_1       | student_2     |  credit_4     |
| course_1       | student_3     |  credit_1     |
| course_1       | student_3     |  credit_2     |
| course_1       | student_3     |  credit_3     |
| course_1       | student_3     |  credit_4     |
| course_2       | student_1     |  credit_1     |
| course_2       | student_1     |  credit_2     |
| course_2       | student_1     |  credit_3     |
| course_2       | student_1     |  credit_4     |
| course_2       | student_2     |  credit_1     |
| course_2       | student_2     |  credit_2     |
| course_2       | student_2     |  credit_3     |
| course_2       | student_2     |  credit_4     |
| course_2       | student_3     |  credit_1     |
| course_2       | student_3     |  credit_2     |
| course_2       | student_3     |  credit_3     |
...........

我想要将每个学生的所有学分归为一组的数据，所以看起来像这样

| course_name  |    student_name  | credit_type                              |
| course_1     |    student_1     | credit_2, credit_3, credit_4             |
| course_1     |    student_2     | credit_1, credit_2, credit_3, credit_4   |
| course_1     |    student_3     | credit_1, credit_3, credit_4             |
| course_2     |    student_1     | credit_1, credit_2, credit_4             |
| course_2     |    student_2     | credit_1, credit_2, credit_4             |
| course_2     |    student_3     | credit_1, credit_2, credit_4             |
| ............ |    ..............| ..., ..., ..., ..., ..., ..., ..., ..., .|

我知道GROUP_CONCAT，只是不确定在这种情况下如何实现它。请记住，这是一个遗留系统，很快就会被淘汰。

最简单的方法是什么？

如果您能帮助我，我将非常感谢。

Answer 1

您只需在此处的两列（GROUP BY）上course_name, student_name：

SELECT
  course_name, 
  student_name, 
  GROUP_CONCAT(credit_type)
FROM your_table
GROUP BY course_name, student_name

如何将具有许多这种关系的列分组？

1 个答案: