在找不到符合我需要的任何内容后,我编写了这段代码以始终如一地随机排列 mysql 中列的值。有更好的方法吗?
**Original table:**
+----+-----------+
| id | fname |
+----+-----------+
| 1 | mike |
| 2 | ricky |
| 3 | jane |
| 4 | august |
| 6 | dave |
| 9 | Jérôme |
+----+-----------+
**Possible output:**
+----+-----------+
| id | fname |
+----+-----------+
| 1 | dave |
| 2 | jane |
| 3 | mike |
| 4 | ricky |
| 6 | Jérôme |
| 9 | august |
+----+-----------+
DROP TEMPORARY TABLE IF EXISTS shuffle1;
DROP TEMPORARY TABLE IF EXISTS shuffle2;
CREATE TEMPORARY TABLE shuffle1 (id int(11) NOT NULL AUTO_INCREMENT, PRIMARY KEY (id), original_values varchar(255), key original_values(original_values) );
CREATE TEMPORARY TABLE shuffle2 (id int(11) NOT NULL AUTO_INCREMENT, PRIMARY KEY (id), original_ids int(11), key original_ids(original_ids) );
INSERT INTO shuffle1 (id, original_values) SELECT NULL, table1.fname FROM table1 ORDER BY rand();
INSERT INTO shuffle2 (id, original_ids) SELECT NULL, table1.id FROM table1;
UPDATE table1 SET table1.fname = (SELECT shuffle1.original_values FROM shuffle1 JOIN shuffle2 ON shuffle2.id = shuffle1.id WHERE table1.id = shuffle2.original_ids);
最佳答案
如果您不介意某些表数据无法处理(取决于表大小,预计 50% 的行无法处理),这里有一个解决方案:
原始表格
id name
1 Some
2 Body
3 Once
4 Told
5 Me
6 The
7 World
8 Is
9 Gonna
10 Roll
11 Me
12 I
13 Ain't
14 The
15 Shapest
16 Tool
17 In
18 The
19 Shed
20 She
21 was
22 looking
23 kind
24 of
25 dumb
26 with
27 her
28 finger
29 and
30 her
31 thumb
查询:
SELECT new_id, name FROM (
SELECT new_id, name FROM (
SELECT new_meme.id as new_id, original_meme.id as original_id, original_meme.name FROM meme original_meme
JOIN meme new_meme ON new_meme.id <> original_meme.id
ORDER BY RAND()
) layer1
GROUP BY layer1.new_id
) layer2 GROUP BY name
结果(当然每次运行都不同)
1 I
2 In
3 Gonna
4 Ain't
5 The
6 her
7 finger
8 Some
9 dumb
10 She
15 Me
16 with
17 Told
18 and
19 World
21 Roll
22 The
25 Tool
26 Shed
27 Is
28 Me
29 Sharpest
31 The
注意:您可能会发现查询非常慢,这是因为它连接了两次表,所以如果数据大小为1000,则需要处理1000 * 1000.
您可以通过更改 ON new_meme.id <> original_meme.id
来控制查询速度至 ON new_meme.id BETWEEN original_meme.id - 5 AND original_meme.id +5
(5 可以更改),但它会降低随机性并且不适用于非数字 id
关于mysql - 如何在 MySql 中打乱一列,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/18518594/