mysql - 如何在 MySQL 中向上移动列的值？

Question

这就是我的 table 的样子:

表名称:以下

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

但是如果更改一个值，例如:

+----+-------+-------+-------+-------+
| 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(以及低于该值的其他值)上升，并且中间不留有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 |
+----+-------+-------+-------+-------+

我厌倦了这个查询:

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

但我收到一些错误错误代码 1,292，SQLState 22007] 截断不正确的 DOUBLE 值:user2

Answer 1

我不知道mysql中的查询是如何编写的，但是这里有一个方法可以实现它。

拳头:

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

第二:

编写一个循环 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.