mysql - 播种 SQLite RANDOM()

Question

SQLite 是否支持播种 RANDOM() 的功能与 MySQL 对 RAND() 的处理方式相同?

$query = "SELECT * FROM table ORDER BY RAND(" . date('Ymd') . ") LIMIT 1;";

来自关于 RAND(N) 的 MySQL 手册:

If a constant integer argument N is specified, it is used as the seed value, which produces a repeatable sequence of column values. In the following example, note that the sequences of values produced by RAND(3) is the same both places where it occurs.

如果没有，有没有办法只使用一个查询来归档相同的效果？

Answer 1

看看 sqlite3_randomness()功能:

SQLite contains a high-quality pseudo-random number generator (PRNG) used to select random ROWIDs when inserting new records into a table that already uses the largest possible ROWID. The PRNG is also used for the build-in random() and randomblob() SQL functions.

...

The first time this routine is invoked (either internally or by the application) the PRNG is seeded using randomness obtained from the xRandomness method of the default sqlite3_vfs object. On all subsequent invocations, the pseudo-randomness is generated internally and without recourse to the sqlite3_vfs xRandomness method.

查看这个xRandomness方法的源码，可以看到它是从Unix上的/dev/urandom读取的。在 Windows 上，它只是返回一些时间函数的返回值。因此，看来您唯一的选择就是开始破解 SQLite 源代码。