如何在MySQL中移动列的值？

Question

这就是我的表格：

表名：关注

+----+-------+-------+-------+-------+
| ID | user1 | user2 | user3 | user4 |
+----+-------+-------+-------+-------+
| 1  | user2 | user1 | user2 | user2 |
| 2  | user3 | user3 | user1 | user3 |
| 3  | user4 | user4 | user4 | user1 |
+----+-------+-------+-------+-------+

但如果改变一个值，如：

+----+-------+-------+-------+-------+
| ID | user1 | user2 | user3 | user4 |
+----+-------+-------+-------+-------+
| 1  | user2 | user1 | user2 | user2 |
| 2  | user3 | user3 | null  | user3 |
| 3  | user4 | user4 | user4 | user1 |
+----+-------+-------+-------+-------+

如何使值user4（及其下面的其他值）上升，两者之间没有 NULL 值？ 我希望输出为：

+----+-------+-------+-------+-------+
| ID | user1 | user2 | user3 | user4 |
+----+-------+-------+-------+-------+
| 1  | user2 | user1 | user2 | user2 |
| 2  | user3 | user3 | user4 | user3 |
| 3  | user4 | user4 | null  | user1 |
+----+-------+-------+-------+-------+

我厌倦了这个问题：

UPDATE following t1
LEFT OUTER JOIN following t2 ON T1.user3+1=T2.user3 - 2
SET t1.user3 = t2.user3;

但是我收到了一些错误Error code 1,292, SQLState 22007] Truncated incorrect DOUBLE value: user2

Answer 1

我不知道如何在mysql中编写查询，但这里有一种方法可以实现它。

拳头：

You show get the Min(ID) and Max(ID).

第二：

Write a loop For i = Min(ID) to Max(ID)

第三：

Update Following set user3 = (Select user3 from Following where ID = i+1) where ID = i 

第四：

Set the last one row data to null or something else what you want init.

Answer 2

您需要创建一个包含可用非空名称的有序列表

SQL DEMO

UPDATE Table1 
LEFT JOIN ( SELECT `ID`,
                   `user3`,
                   @rn := @rn + 1 as rn
            FROM Table1 
            CROSS JOIN ( SELECT @rn := 0 ) as vars
            WHERE `user3` IS NOT NULL
            ORDER BY `ID` ) news
  ON Table1.`ID` = news.rn
SET Table1.`user3` = news.`user3`; 

<强>输出

注意：这里我假设ID是连续序列。如果不是这种情况，您需要创建一个时间id列来进行连接。