SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    747, 746, 927, 924, 930, 904, 961, 962, 
    963, 964, 965, 966, 967, 968, 969, 970, 
    972, 971, 973, 902
  )

Query time 0.00073

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_categories range parent parent 3 40 Using index condition

Result

category_id parent_id
814 902
813 902
808 902
998 902
999 902
1000 902
1001 902
1002 902
1003 902
1004 902
1005 902
1006 902
1007 902
1008 902
1009 902