MYSQL教程mysql 实现互换表中两列数据方法简单实例

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本文介绍了MYSQL教程mysql 实现互换表中两列数据方法简单实例，希望对您有用。如果有疑问，可以联系我们。

MYSQL应用由于最近项目,有这样一个需求,是把数据库中的两列数据互换,经过好久才搞定,这里写个简单实例,做过记录.

MYSQL应用1.创建表及记录用于测试

MYSQL应用
CREATE TABLE `product` (
 `id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT '产品id',`name` varchar(50) NOT NULL COMMENT '产品名称',`original_price` decimal(5,2) unsigned NOT NULL COMMENT '原价',`price` decimal(5,2) unsigned NOT NULL COMMENT '现价',PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `product` (`id`,`name`,`original_price`,`price`) VALUES 
(NULL,'雪糕','5','3.5'),(NULL,'鲜花','18','15'),'甜点','25','12.5'),'玩具','55','45'),'钱包','285','195');

MYSQL应用
mysql> select * from product;
+----+--------+----------------+--------+
| id | name  | original_price | price |
+----+--------+----------------+--------+
| 1 | 雪糕  |      5.00 |  3.50 |
| 2 | 鲜花  |     18.00 | 15.00 |
| 3 | 甜点  |     25.00 | 12.50 |
| 4 | 玩具  |     55.00 | 45.00 |
| 5 | 钱包  |     285.00 | 195.00 |
+----+--------+----------------+--------+
5 rows in set (0.00 sec)

MYSQL应用2.互换original_price与price的值

MYSQL应用新手可能会使用以下方法进行互换

MYSQL应用update product set original_price=price,price=original_price;

MYSQL应用但这样执行的结果只会使original_price与price的值都是price的值,因为update有顺序的,

MYSQL应用先执行original_price=price ,original_price的值已经更新为price,

MYSQL应用然后执行price=original_price,这里相当于没有更新.

MYSQL应用执行结果：

MYSQL应用
mysql> select * from product;
+----+--------+----------------+--------+
| id | name  | original_price | price |
+----+--------+----------------+--------+
| 1 | 雪糕  |      5.00 |  3.50 |
| 2 | 鲜花  |     18.00 | 15.00 |
| 3 | 甜点  |     25.00 | 12.50 |
| 4 | 玩具  |     55.00 | 45.00 |
| 5 | 钱包  |     285.00 | 195.00 |
+----+--------+----------------+--------+
5 rows in set (0.00 sec)
mysql> update product set original_price=price,price=original_price;
Query OK,5 rows affected (0.00 sec)
Rows matched: 5 Changed: 5 Warnings: 0
mysql> select * from product;
+----+--------+----------------+--------+
| id | name  | original_price | price |
+----+--------+----------------+--------+
| 1 | 雪糕  |      3.50 |  3.50 |
| 2 | 鲜花  |     15.00 | 15.00 |
| 3 | 甜点  |     12.50 | 12.50 |
| 4 | 玩具  |     45.00 | 45.00 |
| 5 | 钱包  |     195.00 | 195.00 |
+----+--------+----------------+--------+
5 rows in set (0.00 sec)

MYSQL应用正确的互换方法如下：

MYSQL应用update product as a,product as b set a.original_price=b.price,a.price=b.original_price where a.id=b.id;

MYSQL应用执行结果：

MYSQL应用mysql> select * from product;
+----+--------+----------------+--------+
| id | name?? | original_price | price? |
+----+--------+----------------+--------+
|? 1 | 雪糕?? |?????????? 5.00 |?? 3.50 |
|? 2 | 鲜花?? |????????? 18.00 |? 15.00 |
|? 3 | 甜点?? |????????? 25.00 |? 12.50 |
|? 4 | 玩具?? |????????? 55.00 |? 45.00 |
|? 5 | 钱包?? |???????? 285.00 | 195.00 |
+----+--------+----------------+--------+
5 rows in set (0.00 sec)

MYSQL应用mysql> update product as a,a.price=b.original_price where a.id=b.id;
Query OK,5 rows affected (0.01 sec)
Rows matched: 5? Changed: 5? Warnings: 0

MYSQL应用mysql> select * from product;
+----+--------+----------------+--------+
| id | name?? | original_price | price? |
+----+--------+----------------+--------+
|? 1 | 雪糕?? |?????????? 3.50 |?? 5.00 |
|? 2 | 鲜花?? |????????? 15.00 |? 18.00 |
|? 3 | 甜点?? |????????? 12.50 |? 25.00 |
|? 4 | 玩具?? |????????? 45.00 |? 55.00 |
|? 5 | 钱包?? |???????? 195.00 | 285.00 |
+----+--------+----------------+--------+
5 rows in set (0.00 sec)

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