如何随机排序所选行（真正）？

Currently, I am using this query in my PHP script:

SELECT * FROM `ebooks` WHERE `id`!=$ebook[id] ORDER BY RAND() LIMIT 125;

The database will be about 2500 rows big at max, but I've read that ORDER BY RAND() eventually will slow down the processing time as the data in the database grows.

So I am looking for an alternate method for my query to make things still run smoothly.

Also, I noticed that ORDER BY RAND() is not truly randomizing the rows, because often I see that it follows some kind of pattern that sometimes repeats over and over again.

Is there any method to truly randomize the rows?

The RAND() function is a pseudo-random number generator and if you do not initialize it with different values will give you the same sequence of numbers, so what you should do is:

SELECT * FROM `ebooks` WHERE `id`!=$ebook[id] ORDER BY RAND(UNIX_TIMESTAMP()) LIMIT 125;

which will seed the random number generator from the current time and will give you a different sequence of numbers.

RAND() will slow down the SELECT's ORDER BY clause since it has to generate a random number every time and then sort by it. I would suggest you have the data returned to the calling program and randomize it there using something like array_rand.