SELECT 
  DISTINCT `G`.* 
FROM 
  `cscart_gifts` AS `G` 
  LEFT JOIN `cscart_product_gifts` AS `PG` ON `G`.`gift_id` = `PG`.`gift_id` 
WHERE 
  `PG`.`product_id` = 26521

Query time 0.00036

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "5.59"
    },
    "duplicates_removal": {
      "using_temporary_table": true,
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "G",
            "access_type": "ALL",
            "possible_keys": [
              "PRIMARY"
            ],
            "rows_examined_per_scan": 6,
            "rows_produced_per_join": 6,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.25",
              "eval_cost": "0.60",
              "prefix_cost": "0.85",
              "data_read_per_join": "3K"
            },
            "used_columns": [
              "gift_id",
              "title",
              "icon",
              "text"
            ]
          }
        },
        {
          "table": {
            "table_name": "PG",
            "access_type": "eq_ref",
            "possible_keys": [
              "new_cscart_product_gifts_pk"
            ],
            "key": "new_cscart_product_gifts_pk",
            "used_key_parts": [
              "gift_id",
              "product_id"
            ],
            "key_length": "8",
            "ref": [
              "dev2.G.gift_id",
              "const"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 6,
            "filtered": "100.00",
            "using_index": true,
            "distinct": true,
            "cost_info": {
              "read_cost": "4.14",
              "eval_cost": "0.60",
              "prefix_cost": "5.59",
              "data_read_per_join": "96"
            },
            "used_columns": [
              "product_id",
              "gift_id"
            ]
          }
        }
      ]
    }
  }
}