SELECT 
  category_id, 
  yml2_market_category 
FROM 
  cscart_categories 
WHERE 
  category_id IN ('166', '196', '237') 
  AND yml2_market_category != ''

Query time 0.00167

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "7.21"
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "p_category_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "category_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 3,
      "rows_produced_per_join": 2,
      "filtered": "90.00",
      "index_condition": "(`44mm_ru`.`cscart_categories`.`category_id` in ('166','196','237'))",
      "cost_info": {
        "read_cost": "6.67",
        "eval_cost": "0.54",
        "prefix_cost": "7.21",
        "data_read_per_join": "11K"
      },
      "used_columns": [
        "category_id",
        "yml2_market_category"
      ],
      "attached_condition": "(`44mm_ru`.`cscart_categories`.`yml2_market_category` <> '')"
    }
  }
}