如何在SQL中串联垂直单元格值

Question

我是SQL的新手，我想知道是否有一种方法可以连接单元格值。

例如，我想转换下表：

+---------------------+------------------+
|   student1          |    Mathematics   |
|   student1          |    Science       |
|   student1          |    English       |
|   student2          |    Mathematics   |
|   student2          |    English       |
+---------------------+------------------+

放入如下所示的表中：

+---------------------+------------------------------------+
|   student1          |    Mathematics, Science, English   |
|   student2          |    Mathematics, English            |
+---------------------+------------------------------------+

谢谢

Answer 1

你想要group_concat()

select student, group_concat(subject, ', ') as subjects
from t
group by student;

在SQL Server中，等效项使用string_agg()

select student, string_agg(subject, ', ') as subjects
from t
group by student;

Answer 2

使用group_concat()

select col1, group_concat(col2,', ') from tablename
group by col1