仅在单个表的一行中添加多行

Question

如何通过mysql连接一行中的多行？

示例：

学生表

Sno.| Name  |  Subjects
1.  | ABC   |  English
2.  | ABC   |  Mathematics
3.  | ABC   |  Science
4.  | FMC |  French
5.  | ABC   |  Russian
6.  | JBC   |  French

现在我希望它是这样的格式

Sno.| Name |   Sub1 |  Sub2 | Sub3 |  Sub4 |
1.  | ABC |   Eng  |  Maths| Science| Russian
2.  | FMC |    French| Null| Null   | Null
3.  | JBC |   French| Null | Null   | Null

我不确定到底该怎么做？我应该创建一个视图还是一个表？

我想能看到风景就可以了。

Answer 1

我同意其他的答案，GROUP_CONCAT和PHP一起拆分逗号分隔值可能是最好的方法，但是如果你出于任何其他原因需要通过Pure SQL建议的输出，我会建议以下方法之一。

SELECT  t1.Name, 
        MIN(t1.Subject) AS Sub1,
        MIN(t2.Subject) AS Sub2,
        MIN(t3.Subject) AS Sub3,
        MIN(t4.Subject) AS Sub4
FROM    Students t1
        LEFT JOIN Students T2 
            ON t1.Name = t2.Name 
            AND t2.Subject > t1.Subject
        LEFT JOIN Students T3 
            ON t2.Name = t3.Name 
            AND t3.Subject > t2.Subject
        LEFT JOIN Students T4 
            ON t3.Name = t4.Name 
            AND t4.Subject > t3.Subject
GROUP BY t1.Name;

SELECT   Name,
         MAX(IF(RowNum = 1,Subject, NULL)) AS Sub1,
         MAX(IF(RowNum = 2,Subject, NULL)) AS Sub2,
         MAX(IF(RowNum = 3,Subject, NULL)) AS Sub3,
         MAX(IF(RowNum = 4,Subject, NULL)) AS Sub4
FROM     (    SELECT   Name,
                       Subject,
                       @r:= IF(@Name = Name, @r + 1, 1) AS RowNum,
                       @Name:= Name AS Name2
              FROM    Students,
                      (SELECT @Name:='') n,
                      (SELECT @r:= 0) r
              ORDER BY Name, Sno
          ) t
GROUP BY Name

Answer 2

使用以下查询，获取姓名和他/她的主题。

SELECT Name, GROUP_CONCAT(Subjects) AS List
FROM myTable
GROUP BY Name

然后，在PHP中，您可以使用函数打印主题。

希望这能有所帮助。

Demo at sqlfiddle

Answer 3

尝试使用GROUP BY和GROUP_CONCAT

SELECT Name, GROUP_CONCAT(Subjects) AS Subjects_list
FROM students_table
GROUP BY Name

然后在获取记录时使用PHP函数explode来获取存储在Subjects_list列中的不同值。