SELECT 
  a.category_id 
FROM 
  cscart_categories as a 
  LEFT JOIN cscart_categories as b ON b.category_id IN (412) 
WHERE 
  a.id_path LIKE CONCAT(b.id_path, '/%')

Query time 0.00043

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE b const PRIMARY,p_category_id,idx_category_id PRIMARY 3 const 1
1 SIMPLE a ALL 415 Using where

Result

category_id
898
897
899
461
900
468
432
482
890
937
922
925
929
938
939
940
941
942
943
944
945
946
947
974
975
976
977
978
979
980
981
982
983
984
985