Insert unique random number with recursive MySQL - mysql

Question

I want to populate a table with unique random numbers without using a procedure.
I've tried using this reply to do it but not success.
What I'm trying to do is something like this but validating that numbers are not repeated:
INSERT into table (row1,row2)
WITH RECURSIVE
cte AS ( SELECT 0 num, LPAD(FLOOR(RAND() * 99999999),8,0) random_num
UNION ALL
SELECT num+1, LPAD(FLOOR(RAND() * 99999999),8,0) random_num
FROM cte WHERE num < 100000-1)
SELECT random_num, null
FROM cte;
In the example above, I am able to generate random values and insert them but without validating that the numbers are not repeated.
I have tried to do this:
INSERT into table (row1,row2)
WITH RECURSIVE
cte AS ( SELECT 0 num, LPAD(FLOOR(RAND() * 99999999),8,0) random_num
UNION ALL
SELECT num+1, LPAD(FLOOR(RAND() * 99999999),8,0) random_num
FROM cte WHERE num < 100000-1 AND random_num NOT IN (SELECT random_num FROM cte WHERE random_num IS NOT NULL))
SELECT random_num, null
FROM cte;
but the condition AND random_num NOT IN (SELECT random_num FROM cte WHERE random_num IS NOT NULL) in the where case, causes an SQL Error [4008] [HY000]: Restrictions imposed on recursive definitions are violated for table 'cte'
Any suggestions of how to do it? thank you!.

Answer 1

This could be an option. Generate all possible values, sort randomly and take desired number of entries.
CREATE TABLE random_data (
row1 INT PRIMARY KEY AUTO_INCREMENT,
row2 VARCHAR(10) NOT NULL,
UNIQUE KEY _Idx1 ( row2 )
);
INSERT INTO random_data (row2)
SELECT LPAD(num, 8, 0)
FROM (
SELECT h * 10000000 + g * 1000000 + f * 100000 + e * 10000 + d * 1000 + c * 100 + b * 10 + a AS num
FROM (SELECT 0 a UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) ta
JOIN (SELECT 0 b UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) tb
JOIN (SELECT 0 c UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) tc
JOIN (SELECT 0 d UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) td
JOIN (SELECT 0 e UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) te
JOIN (SELECT 0 f UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) tf
JOIN (SELECT 0 g UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) tg
JOIN (SELECT 0 h UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) th
) n
ORDER BY RAND()
LIMIT 100000;

Answer 2

If you have a table - any table - with e.g. 100 rows then you can generate million distinct random numbers between 0 and 99999999 as follows:
select distinct floor(rand() * 100000000)
from t as t0, t as t1, t as t2
limit 1000000
Note that because of distinct you will need to generate a bigger number of rows so that you get desired number of rows after distinct.