如何在MySQL中删除一行并重新排序其他行的正确ID？

为了理解这个概念，让我们先创建一个表。创建表的查询语句如下：

mysql> create table ReorderSortDemo
   -> (
   -> UserId int
   -> );
Query OK, 0 rows affected (0.57 sec)

使用insert命令在表中插入一些记录。查询语句如下：

mysql> insert into ReorderSortDemo values(14);
Query OK, 1 row affected (0.13 sec)
mysql> insert into ReorderSortDemo values(4);
Query OK, 1 row affected (0.10 sec)
mysql> insert into ReorderSortDemo values(6);
Query OK, 1 row affected (0.11 sec)
mysql> insert into ReorderSortDemo values(3);
Query OK, 1 row affected (0.09 sec)
mysql> insert into ReorderSortDemo values(8);
Query OK, 1 row affected (0.11 sec)
mysql> insert into ReorderSortDemo values(18);
Query OK, 1 row affected (0.08 sec)
mysql> insert into ReorderSortDemo values(1);
Query OK, 1 row affected (0.12 sec)
mysql> insert into ReorderSortDemo values(11);
Query OK, 1 row affected (0.08 sec)
mysql> insert into ReorderSortDemo values(16);
Query OK, 1 row affected (0.09 sec)

使用select语句显示表中的所有记录。查询语句如下：

mysql> select *from ReorderSortDemo;

输出是：

+--------+
| UserId |
+--------+
|     14 |
|      4 |
|      6 |
|      3 |
|      8 |
|     18 |
|      1 |
|     11 |
|     16 |
+--------+
9 rows in set (0.00 sec)

先从表中删除一行，然后使用update命令重新排序其他行。查询语句如下：

mysql> delete from ReorderSortDemo where UserId=8;
Query OK, 1 row affected (0.20 sec)

删除后，再次检查表中的记录。查询语句如下：

mysql> select *from ReorderSortDemo;

输出是：

+--------+
| UserId |
+--------+
|     14 |
|      4 |
|      6 |
|      3 |
|     18 |
|      1 |
|     11 |
|     16 |
+--------+
8 rows in set (0.00 sec)

以下是重新排序其他列的查询语句：

mysql> update ReorderSortDemo
   -> set UserId=UserId-1
   -> where UserId > 8;
Query OK, 4 rows affected (0.22 sec)
Rows matched: 4 Changed: 4 Warnings: 0

再次检查表中的记录。查询语句如下：

mysql> select *from ReorderSortDemo;

输出是：

+--------+
| UserId |
+--------+
|     13 |
|      4 |
|      6 |
|      3 |
|     17 |
|      1 |
|     10 |
|     15 |
+--------+
8 rows in set (0.00 sec)