Sandbox

SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.short_description, 
  IF(
    cscart_product_descriptions.short_description = '' 
    OR cscart_product_descriptions.short_description IS NULL, 
    cscart_product_descriptions.full_description, 
    ''
  ) AS full_description 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (415241) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00045

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.00"
    },
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "const",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "9",
      "ref": [
        "const",
        "const"
      ],
      "rows_examined_per_scan": 1,
      "rows_produced_per_join": 1,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "0.00",
        "eval_cost": "0.20",
        "prefix_cost": "0.00",
        "data_read_per_join": "6K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ]
    }
  }
}

Result

product_id	short_description	full_description
415241		<p>Graduated dispenser for cake dough</p> <p>Enjoy pancakes, muffins and cakes without the mess. When used as a dough dispenser, it allows a precise placement directly on the tray, pan or wherever the dough is needed.</p> <p>The spring-loaded handle opens and closes the dispenser nozzle to help adjust the size of all your baked goods;</p> <p>Children love to use it as a dough dispenser for the oven due to its fun and easy design;</p> <p>This mess-free baking tool comes with a locking lid and is made of durable plastic;</p> <p>Spend more time enjoying your baked goods and less time cleaning up with the Batter Dispenser;</p> <p>The device has a capacity of up to 4 cups or 900 ml of dough.</p><p></p>