MySQL的随机选出的id值很小

Question

我在尝试随机取出mysql中的一条数据中

DESCRIBE nickname_library;

+-------+-------------+------+-----+---------+----------------+
| Field | Type        | Null | Key | Default | Extra          |
+-------+-------------+------+-----+---------+----------------+
| id    | int         | NO   | PRI | NULL    | auto_increment |
| name  | varchar(10) | NO   | UNI | NULL    |                |
+-------+-------------+------+-----+---------+----------------+

以下用来证明字段id是连续且自增的:

SELECT MIN(id), MAX(id), COUNT(*) FROM `nickname_library`;

+---------+---------+----------+
| min(id) | max(id) | count(*) |
+---------+---------+----------+
|       1 |    2415 |     2415 |
+---------+---------+----------+

但是我尝试执行:

SELECT * FROM `nickname_library`
WHERE id >= (
    SELECT FLOOR(RAND() * (SELECT MAX(id) FROM `nickname_library`))
) 
ORDER BY id LIMIT 10;

+-----+-----------------------+
| id  | name                  |
+-----+-----------------------+
|  36 | 青衫不改旧人还        |
|  63 | 和晨濡                |
|  80 | 倦怠                  |
|  86 | 勉励                  |
|  92 | 梦                    |
| 148 | 超越                  |
| 160 | 叶觞彡                |
| 167 | 装乖很简单            |
| 208 | 安知                  |
| 224 | 沐樱                  |
+-----+-----------------------+

这里的id居然不是连续的，而且我试了很多次，选出来的id一直没有超过300
可是我的数据一共有2415条数据
但是我单独执行:

SELECT FLOOR(RAND() * (SELECT MAX(id) FROM `nickname_library`));

选出的数据又是很平均的

+----------------------------------------------------------+
| FLOOR(RAND() * (SELECT MAX(id) FROM `nickname_library`)) |
+----------------------------------------------------------+
|                                                      451 |
+----------------------------------------------------------+
+----------------------------------------------------------+
| FLOOR(RAND() * (SELECT MAX(id) FROM `nickname_library`)) |
+----------------------------------------------------------+
|                                                     1912 |
+----------------------------------------------------------+
+----------------------------------------------------------+
| FLOOR(RAND() * (SELECT MAX(id) FROM `nickname_library`)) |
+----------------------------------------------------------+
|                                                      965 |
+----------------------------------------------------------+

求解答

Answer 1

个人理解，仅供参考：

如图所示，按照你的逻辑的话，应该只会产生一个数值，但是rand()会被计算多次，所以产生了四个值，至于为什么rand()会被执行多次，可以参考下面这个文章
https://www.coder.work/article/3997356