MySQL ORDER BY RAND() LIMIT and combine

I have 2 tables (tmp1,tmp2). Every table contains unique (product)_id's only. I need to create a query to get a fixed and random number of ID's from table tmp2 for each ID from table tmp1. I've tried it with GROUP_CONCAT, but get's error:

SELECT p.products_id,
GROUP_CONCAT((SELECT tmp2.products_id FROM tmp2 tmp2 ORDER BY RAND() LIMIT 12))
FROM tmp1 tmp1
GROUP BY tmp1.products_id

LIMIT 1

"subquery returned more than one record"

That's the result I need.

example:

---

ID tmp1 | ID tmp2

1 | 103,204,867,547,354,514,541

2 | 542,245,876,542,681,248,428