Question

我有2个表，学生表，其中包含 regNo 和 name 列；和 reg_subject 表，其中包含学生单独注册的科目列表。一个学生可以注册多个科目。

我想生成一个将两个表连接起来的表，以便将 reg_subject 表转置，使行变成列。下面概述了这两个表以及结果表。

学生桌

| regNo | name  |
_________________
| 1001  | Saleh |
-----------------
| 1002  | Moses |
-----------------
| 1003  | Hafsa |

reg_subject表

| regNo | subject  |
____________________
| 1001  | English  |
--------------------
| 1001  | Math     |
--------------------
| 1002  | English  |
--------------------
| 1003  | Math     |
--------------------
| 1002  | Math     |
--------------------
| 1003  | Physics  |
--------------------
| 1001  | Physics  |
--------------------
| 1002  | Physics  |
--------------------

转置的联接表应如下所示：

The transposed joint table

| regNo | name  | subject1 | subject2 | subject3 |
__________________________________________________
| 1001  | Saleh | English  | Math     | Physics  |
--------------------------------------------------
| 1002  | Moses | English  | Math     | Physics  |
--------------------------------------------------
| 1003  | Hafsa |          | Math     | Physics  |
--------------------------------------------------

Answer 1

 SELECT regNo, name,               
        MAX( CASE WHEN subject = 'English'
                  THEN subject
             END) as subject1,
        MAX( CASE WHEN subject = 'Math'
                  THEN subject
             END) as subject2,
        MAX( CASE WHEN subject = 'Physics'
                  THEN subject
             END) as subject3
FROM YourTable
GROUP BY regNo, name

将重复的行转置为mysql中的列

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