Question

我有一个名为users（25k记录）的数据库表

我有一个名为“阿凡达”的字段

我需要更新此字段，从列表中分配一个随机网址

列出网址：

http://myserver.com/img/1.png
http://myserver.com/img/2.png
http://myserver.com/img/3.png
http://myserver.com/img/4.png
http://myserver.com/img/5.png
http://myserver.com/img/6.png
http://myserver.com/img/7.png
http://myserver.com/img/8.png
http://myserver.com/img/9.png
http://myserver.com/img/10.png
http://myserver.com/img/11.png
http://myserver.com/img/12.png
http://myserver.com/img/13.png
http://myserver.com/img/14.png
http://myserver.com/img/15.png

我有这段代码：

UPDATE TABLE SET VALUE=VALUE+ROUND(1+RAND()*4);

我该如何调整此查询？

Answer 1

如果您的图片遵循漂亮的图案，@ itterm的答案很好，但您也可以从列表中选择一个随机字符串：

SELECT ELT(ROUND(0.5+RAND()*15), 
 'http://myserver.com/img/1.png',
 'http://myserver.com/img/2.png',
 'http://myserver.com/img/3.png',
 'http://myserver.com/img/4.png',
 'http://myserver.com/img/5.png',
 'http://myserver.com/img/6.png',
 'http://myserver.com/img/7.png',
 'http://myserver.com/img/8.png',
 'http://myserver.com/img/9.png',
 'http://myserver.com/img/10.png',
 'http://myserver.com/img/11.png',
 'http://myserver.com/img/12.png',
 'http://myserver.com/img/13.png',
 'http://myserver.com/img/14.png',
 'http://myserver.com/img/15.png') AS avatar;

请参阅http://dev.mysql.com/doc/refman/5.6/en/string-functions.html#function_elt

要更新表，可以在UPDATE语句中使用相同的ELT()表达式：

UPDATE TABLE SET AVATAR=ELT(...);

Answer 2

你在找这样的东西吗？

UPDATE users
   SET avatar = CONCAT('http://myserver.com/img/', FLOOR(1 + RAND() * 15), '.png');

这是 SQLFiddle 演示

虽然我建议只存储整数部分，但如果你需要存储它，

UPDATE users
   SET avatar = FLOOR(1 + RAND() * 15);

SELECT id, CONCAT('http://myserver.com/img/', avatar, '.png') avatar
  FROM users;

这是 SQLFiddle 演示

然后在您选择数据时动态构建一个头像网址，或者更好地在您的客户端代码中执行此操作（从某种设置获取域名和路径）

SELECT id, CONCAT('http://myserver.com/img/', FLOOR(1 + RAND() * 15), '.png') avatar
  FROM users;

这是 SQLFiddle 演示

使用列表中的随机链接更新列

2 个答案: