SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    166, 167, 203, 223, 219, 228, 241, 245, 
    250
  ) 
  AND category_id != 264

Query time 0.00062

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_categories",
      "access_type": "ALL",
      "possible_keys": ["PRIMARY", "parent", "p_category_id"],
      "rows": 84,
      "filtered": 44.04761887,
      "attached_condition": "cscart_categories.parent_id in (166,167,203,223,219,228,241,245,250) and cscart_categories.category_id <> 264"
    }
  }
}