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 (415240) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00105

JSON explain

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    "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
415240 <p>UV LED 48W Nail Lamp, Digital Display, Timer<br /></p><p>The ultra-modern nail lamp ensures fast and efficient polymerization of UV gels and semi-permanent nail polishes. The very powerful lamp is made according to the latest technologies, so the level of irradiation is very low. It allows the insertion of the 5 fingers of the hand at the same time and has a removable base, to be very effective for pedicures as well.</p> <p>Among the lamp's advantages are its long life, modern design, very high power, fast polymerization of UV gels and semi-permanent nail polishes, low level of radiation.</p> <p>Power 48W DC12V/5A AC110V - 220V, 50/60Hz</p><p></p>