MySQL - 追溯添加ID AUTO_INCREMENTs

Question

我有很多行的表，并且没有id列。我想回去：

1. 与AUTO_INCREMENT
2. 添加ID列PRIMARY KEY更重要的是，回顾添加一个ID为所有现有的行，从最旧到最新（有一个“更新时间”柱）。

有什么建议吗？

Answer 1

让我们看看下面的例子：

CREATE TABLE your_table (some_value int, updatetime datetime); 

INSERT INTO your_table VALUES (100, '2010-08-11 12:09:00'); 
INSERT INTO your_table VALUES (300, '2010-08-11 12:08:00'); 
INSERT INTO your_table VALUES (200, '2010-08-11 12:07:00'); 
INSERT INTO your_table VALUES (400, '2010-08-11 12:06:00'); 
INSERT INTO your_table VALUES (600, '2010-08-11 12:05:00'); 
INSERT INTO your_table VALUES (500, '2010-08-11 12:04:00'); 
INSERT INTO your_table VALUES (800, '2010-08-11 12:03:00'); 

首先，我们可以添加id列：

ALTER TABLE your_table ADD id int unsigned; 

现在的表看起来像这样：

SELECT * FROM your_table; 
+------------+---------------------+------+ 
| some_value | updatetime   | id | 
+------------+---------------------+------+ 
|  100 | 2010-08-11 12:09:00 | NULL | 
|  300 | 2010-08-11 12:08:00 | NULL | 
|  200 | 2010-08-11 12:07:00 | NULL | 
|  400 | 2010-08-11 12:06:00 | NULL | 
|  600 | 2010-08-11 12:05:00 | NULL | 
|  500 | 2010-08-11 12:04:00 | NULL | 
|  800 | 2010-08-11 12:03:00 | NULL | 
+------------+---------------------+------+ 
7 rows in set (0.00 sec) 

然后我们就可以UPDATE行号为id列时

SET @row_number := 0; 

UPDATE your_table 
SET  your_table.id = (@row_number := @row_number + 1) 
ORDER BY your_table.updatetime; 

现在的表看起来像这样：

SELECT * FROM your_table ORDER BY id; 
+------------+---------------------+----+ 
| some_value | updatetime   | id | 
+------------+---------------------+----+ 
|  800 | 2010-08-11 12:03:00 | 1 | 
|  500 | 2010-08-11 12:04:00 | 2 | 
|  600 | 2010-08-11 12:05:00 | 3 | 
|  400 | 2010-08-11 12:06:00 | 4 | 
|  200 | 2010-08-11 12:07:00 | 5 | 
|  300 | 2010-08-11 12:08:00 | 6 | 
|  100 | 2010-08-11 12:09:00 | 7 | 
+------------+---------------------+----+ 

然后，我们可以设置id列作为主键，并使其NOT NULL和AUTO_INCREMENT结果集是由updatetime列排序：

ALTER TABLE your_table 
MODIFY id int unsigned NOT NULL AUTO_INCREMENT, ADD PRIMARY KEY (id); 

这是表的新描述：

DESCRIBE your_table; 
+------------+------------------+------+-----+---------+----------------+ 
| Field  | Type    | Null | Key | Default | Extra   | 
+------------+------------------+------+-----+---------+----------------+ 
| some_value | int(11)   | YES |  | NULL |    | 
| updatetime | datetime   | YES |  | NULL |    | 
| id   | int(10) unsigned | NO | PRI | NULL | auto_increment | 
+------------+------------------+------+-----+---------+----------------+ 
3 rows in set (0.04 sec) 

我们现在可以尝试INSERT表中的一个新行，以确认AUTO_INCREMENT正在按预期：

INSERT INTO your_table (some_value, updatetime) 
VALUES (900, '2010-08-11 12:10:00'); 

SELECT * FROM your_table ORDER BY id; 
+------------+---------------------+----+ 
| some_value | updatetime   | id | 
+------------+---------------------+----+ 
|  800 | 2010-08-11 12:03:00 | 1 | 
|  500 | 2010-08-11 12:04:00 | 2 | 
|  600 | 2010-08-11 12:05:00 | 3 | 
|  400 | 2010-08-11 12:06:00 | 4 | 
|  200 | 2010-08-11 12:07:00 | 5 | 
|  300 | 2010-08-11 12:08:00 | 6 | 
|  100 | 2010-08-11 12:09:00 | 7 | 
|  900 | 2010-08-11 12:10:00 | 8 | 
+------------+---------------------+----+ 
8 rows in set (0.00 sec) 

我不知道是否有解决这个更简单的方法，但这种方法似乎能完成这项工作。