《MYSQL教程mysql 實現互換表中兩列數據方法簡單實例》要點：
本文介紹了MYSQL教程mysql 實現互換表中兩列數據方法簡單實例，希望對您有用。如果有疑問，可以聯系我們。
MYSQL應用由于最近項目,有這樣一個需求,是把數據庫中的兩列數據互換,經過好久才搞定,這里寫個簡單實例,做過記錄.
MYSQL應用1.創建表及記錄用于測試
MYSQL應用
CREATE TABLE `product` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT '產品id',
`name` varchar(50) NOT NULL COMMENT '產品名稱',
`original_price` decimal(5,2) unsigned NOT NULL COMMENT '原價',
`price` decimal(5,2) unsigned NOT NULL COMMENT '現價',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `product` (`id`, `name`, `original_price`, `price`) VALUES
(NULL, '雪糕', '5', '3.5'),
(NULL, '鮮花', '18', '15'),
(NULL, '甜點', '25', '12.5'),
(NULL, '玩具', '55', '45'),
(NULL, '錢包', '285', '195');
MYSQL應用
mysql> select * from product;
+----+--------+----------------+--------+
| id | name | original_price | price |
+----+--------+----------------+--------+
| 1 | 雪糕 | 5.00 | 3.50 |
| 2 | 鮮花 | 18.00 | 15.00 |
| 3 | 甜點 | 25.00 | 12.50 |
| 4 | 玩具 | 55.00 | 45.00 |
| 5 | 錢包 | 285.00 | 195.00 |
+----+--------+----------------+--------+
5 rows in set (0.00 sec)
MYSQL應用2.互換original_price與price的值
MYSQL應用新手可能會使用以下方法進行互換
MYSQL應用update product set original_price=price,price=original_price;
MYSQL應用但這樣執行的結果只會使original_price與price的值都是price的值,因為update有順序的,
MYSQL應用先執行original_price=price , original_price的值已經更新為price,
MYSQL應用然后執行price=original_price,這里相當于沒有更新.
MYSQL應用執行結果：
MYSQL應用
mysql> select * from product;
+----+--------+----------------+--------+
| id | name | original_price | price |
+----+--------+----------------+--------+
| 1 | 雪糕 | 5.00 | 3.50 |
| 2 | 鮮花 | 18.00 | 15.00 |
| 3 | 甜點 | 25.00 | 12.50 |
| 4 | 玩具 | 55.00 | 45.00 |
| 5 | 錢包 | 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 | 鮮花 | 15.00 | 15.00 |
| 3 | 甜點 | 12.50 | 12.50 |
| 4 | 玩具 | 45.00 | 45.00 |
| 5 | 錢包 | 195.00 | 195.00 |
+----+--------+----------------+--------+
5 rows in set (0.00 sec)
MYSQL應用正確的互換方法如下：
MYSQL應用update product as a, product as b set a.original_price=b.price, a.price=b.original_price where a.id=b.id;
MYSQL應用執行結果：
MYSQL應用mysql> select * from product;
+----+--------+----------------+--------+
| id | name?? | original_price | price? |
+----+--------+----------------+--------+
|? 1 | 雪糕?? |?????????? 5.00 |?? 3.50 |
|? 2 | 鮮花?? |????????? 18.00 |? 15.00 |
|? 3 | 甜點?? |????????? 25.00 |? 12.50 |
|? 4 | 玩具?? |????????? 55.00 |? 45.00 |
|? 5 | 錢包?? |???????? 285.00 | 195.00 |
+----+--------+----------------+--------+
5 rows in set (0.00 sec)
MYSQL應用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應用mysql> select * from product;
+----+--------+----------------+--------+
| id | name?? | original_price | price? |
+----+--------+----------------+--------+
|? 1 | 雪糕?? |?????????? 3.50 |?? 5.00 |
|? 2 | 鮮花?? |????????? 15.00 |? 18.00 |
|? 3 | 甜點?? |????????? 12.50 |? 25.00 |
|? 4 | 玩具?? |????????? 45.00 |? 55.00 |
|? 5 | 錢包?? |???????? 195.00 | 285.00 |
+----+--------+----------------+--------+
5 rows in set (0.00 sec)
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