SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(176, 185, 186, 202, 187, 188, 189) 
  AND category_id != 264

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_categories",
          "access_type": "ALL",
          "possible_keys": ["PRIMARY", "parent", "p_category_id"],
          "rows": 11,
          "filtered": 63.63636398,
          "attached_condition": "cscart_categories.parent_id in (176,185,186,202,187,188,189) and cscart_categories.category_id <> 264"
        }
      }
    ]
  }
}