SELECT 
  url 
FROM 
  ushop_seller_banners 
WHERE 
  company_id = 2

Query time 0.00081

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.31"
    },
    "table": {
      "table_name": "ushop_seller_banners",
      "access_type": "ALL",
      "rows_examined_per_scan": 8,
      "rows_produced_per_join": 1,
      "filtered": "12.50",
      "cost_info": {
        "read_cost": "1.21",
        "eval_cost": "0.10",
        "prefix_cost": "1.31",
        "data_read_per_join": "272"
      },
      "used_columns": [
        "company_id",
        "url"
      ],
      "attached_condition": "(`marketplace`.`ushop_seller_banners`.`company_id` = 2)"
    }
  }
}