MySQL 如何交换特定字段值

首先创建一个表如下：

mysql> create table DemoTable
(
    Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
    Number1 int,
    Number2 int
);
Query OK, 0 rows affected (0.68 sec)

使用insert命令向表中插入一些记录：

mysql> insert into DemoTable(Number1,Number2) values(10,30);
Query OK, 1 row affected (0.09 sec)
mysql> insert into DemoTable(Number1,Number2) values(60,50);
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable(Number1,Number2) values(110,100);
Query OK, 1 row affected (0.10 sec)

使用select语句来显示表中的所有记录：

mysql> select *from DemoTable;

这将产生以下输出：

+----+---------+---------+
| Id | Number1 | Number2 |
+----+---------+---------+
|  1 |      10 |      30 |
|  2 |      60 |      50 |
|  3 |     110 |     100 |
+----+---------+---------+
3 rows in set (0.00 sec)

现在，让我们在MySQL中交换特定的字段值。这里，我们交换字段“Number1”和“Number2”，其中Id = 2：

mysql> update DemoTable
    set Number1=(@temporaryVariable:=Number1),
    Number1=Number2,
    Number2=@temporaryVariable
    where Id=2;
Query OK, 1 row affected (0.21 sec)
Rows matched: 1 Changed: 1 Warnings: 0

让我们再次检查表的记录：

mysql> select *from DemoTable;

这将产生以下输出：

+----+---------+---------+
| Id | Number1 | Number2 |
+----+---------+---------+
|  1 |      10 |      30 |
|  2 |      50 |      60 |
|  3 |     110 |     100 |
+----+---------+---------+
3 rows in set (0.00 sec)

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