《MYSQL教程mysql 实现互换表中两列数据方法简单实例》要点：
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'),
(NULL, '甜点', '25', '12.5'),
(NULL, '玩具', '55', '45'),
(NULL, '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, product as b set a.original_price=b.price, 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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