Question

我需要查询我的要求。我有一个名为subject_details的表，它有2个字段。

student_Id  std_subject  
10               physics  
20               physics  
30               English  
10               Maths  
20               chemistry

我想返回以下记录：

 student_id       std_subject  
   10             physics,maths  
   20             physics,chemistry   
   30             English

Answer 1

对于mysql，您可以使用group_concat

select student_id, group_concat(std_subject)
from subject_detials
group by student_id

fiddle

Answer 2

你可以在mysql中使用group_concat。 https://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_group-concat 试试这个：

select student_id as student_id, group_concat(std_subject) as std_subject
from subject_detials
group by student_id

Answer 3

Oracle解决方案：演示 @ ORACLE Fiddle

示例1 ：

SELECT  
  "student_Id",
  RTRIM( XMLAGG( XMLELEMENT( R, "std_subject", ',' )
                .EXTRACT( '//text()' ) ),
         ',' ) subjects
FROM  student_subjects
GROUP BY "student_Id";

结果1 ：

+------------+-------------------+
| student_id | subjects          |
+------------+-------------------+
|         10 | physics,Maths     |
|         20 | physics,chemistry |  
|         30 | English           |
+------------+-------------------+

示例2 ：

SELECT 
  "student_Id",
  RTRIM( LISTAGG( "std_subject" || ',' ) 
         WITHIN GROUP( ORDER BY 1 ),
         ',' ) subjects
FROM  student_subjects
GROUP BY "student_Id";

结果2 ：

+------------+-------------------+
| student_id | subjects          |
+------------+-------------------+
|         10 | Maths,physics     |
|         20 | chemistry,physics |  
|         30 | English           |
+------------+-------------------+

Answer 4

在Oracle DB

中

使用LISTAGG功能（LISTAGG ORACLE DOC）这将做你想要的。

SELECT 
    student_Id
    ,LISTAGG(std_subject, ',') WITHIN GROUP (ORDER BY std_subject) std_subject
FROM 
    student_subjects
GROUP BY 
    student_Id;

在Oracle SQL中，单行显示多行

4 个答案:

在Oracle DB