How to “check” if a function really gives a random

Question

How can one be sure that a function is really random or as close to the notion as possible? Also, what is the distinction between random and pseudo-random? Finally, what algorithms/sources can be used to generate random numbers?

P.S: Also asking this because a MySQL statement using ORDER BY RAND() LIMIT 1 isn't giving convincing results.

Answer 1

True, We can not guarantee the random number is actually a random .
about pseudo-random numbers : yes they just seems to be random ( Originally used in cryptography) (pseudo random functions ), when sending encrypted text and the evil in between traps the message thinks that the encrypted text he got is random, but the message was calculated from some function, moreover you will get the same message using the same function and key ( if any , so no-where they are not random, just look like random because you can not create the original text/number from which it generate. Such as hash functions(md5,sha1) and encryption techniques ( des,aes etc ).