How to Generate Random number without repeat in database using PHP?

Question

I would like to generate a 5 digit number which do not repeat inside the database. Say I have a table named numbers_mst with field named my_number

Answer 1

In addition to Tushar's answer to make it work when numbers_mst is empty:

SELECT random_num
FROM (
  SELECT FLOOR(RAND() * 99999) AS random_num 
  UNION
  SELECT FLOOR(RAND() * 99999) AS random_num
) AS numbers_mst_plus_1
WHERE `random_num` NOT IN (SELECT my_number FROM numbers_mst)
LIMIT 1