Bagaimana cara membatasi banyak angka dengan memfilter beberapa kolom di MySql?

Anda dapat menggunakan UNION query untuk mendapatkan semua pertanyaan Anda sekaligus:

(SELECT * FROM question WHERE categori_id=1 ORDER BY RAND() LIMIT 12)
UNION
(SELECT * FROM question WHERE categori_id=2 ORDER BY RAND() LIMIT 20)
UNION
(SELECT * FROM question WHERE categori_id=3 ORDER BY RAND() LIMIT 10)
UNION
(SELECT * FROM question WHERE categori_id=4 ORDER BY RAND() LIMIT 8)