SELECT 
  combination 
FROM 
  cscart_product_options_inventory 
WHERE 
  product_id = 9470 
  AND amount > 0 
  AND combination != ''

Query time 0.00044

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_product_options_inventory range pc pc 770 6 Using index condition; Using where

Result

combination
1192_22442
1192_22442_1193_22451
1192_22442_1193_22452
1192_22443
1192_22443_1193_22451
1192_22443_1193_22452
1192_22444
1192_22444_1193_22451
1192_22444_1193_22452