Generate random numbers in MySQL and check for randomness for non-repeating behaviour.

p_generate_random_numbers.sql

CREATE TABLE `random_numbers` (
  `random_number` VARCHAR(20) NOT NULL COMMENT 'Random Number',
  PRIMARY KEY (`random_number`),
  KEY `random_number_key` (`random_number`)
);

SELECT LENGTH(RAND()); # Length varies

DROP PROCEDURE IF EXISTS p_generate_random_numbers;
DELIMITER $$  
CREATE PROCEDURE p_generate_random_numbers()
BEGIN
	DECLARE i INT DEFAULT 0;
	insert_loop: LOOP
		INSERT INTO random_numbers(`random_number`) VALUES (RAND());
		SET i = i+1;
		IF i > 5000 THEN
			LEAVE insert_loop;
		END IF;
	END LOOP insert_loop;
END $$

CALL p_generate_random_numbers();

SELECT COUNT(random_number) FROM random_numbers;
SELECT random_number, COUNT(random_number) FROM random_numbers GROUP BY random_number;

# Wow, what a random number! No data here.
SELECT
	random_number,
	COUNT(random_number) repeatetions
FROM random_numbers
GROUP BY random_number
HAVING repeatetions > 1;