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 (
    87020, 87021, 87022, 87023, 87079, 87080, 
    87081, 87082, 87083, 87084, 87130, 
    87131, 87132, 87133, 87134, 87135, 
    86950, 86951, 86952, 86953, 86954, 
    86955, 86956, 87011, 87012, 87013, 
    87014, 87015, 87016, 87017
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00071

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "13.52"
    },
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "9",
      "rows_examined_per_scan": 30,
      "rows_produced_per_join": 30,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "10.52",
        "eval_cost": "3.00",
        "prefix_cost": "13.52",
        "data_read_per_join": "114K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (87020,87021,87022,87023,87079,87080,87081,87082,87083,87084,87130,87131,87132,87133,87134,87135,86950,86951,86952,86953,86954,86955,86956,87011,87012,87013,87014,87015,87016,87017)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
86950 Old London Floor Standing 2 Door Vanity Unit with 1 Tap Hole Black Marble Top 1000mm - Storm Grey
86951 Old London Floor Standing 2 Door Vanity Unit with 1 Tap Hole White Marble Top 1000mm - Storm Grey
86952 Old London Old London Storm Grey Floor Standing 2 Door Vanity Basin Unit with Square Basin & 1 Tap Hole Marble Top, 1000mm - Storm Grey
86953 Old London Floor Standing 2 Door Vanity Unit with 1 Tap Hole Grey Marble Top 1000mm - Storm Grey
86954 Old London Floor Standing 2 Door Vanity Unit with 3 Tap Hole Black Marble Top 1000mm - Storm Grey
86955 Old London Floor Standing 2 Door Vanity Unit with 1 Tap Hole White Marble Top 1000mm - Storm Grey
86956 Old London Floor Standing 2 Door Vanity Unit with 1 Tap Hole Grey Marble Top 1000mm - Storm Grey
87011 Old London Floor Standing 2 Door Vanity Unit with 1 Tap Hole Black Marble Top 1000mm - Twilight Blue
87012 Old London Floor Standing 2 Door Vanity Unit with 1 Tap Hole White Marble Top 1000mm - Twilight Blue
87013 Old London Old London Twilight Blue Floor Standing 2 Door Vanity Basin Unit with Square Basin & 1 Tap Hole Marble Top, 1000mm - Twilight Blue
87014 Old London Floor Standing 2 Door Vanity Unit with 1 Tap Hole Grey Marble Top 1000mm - Twilight Blue
87015 Old London Floor Standing 2 Door Vanity Unit with 3 Tap Hole Black Marble Top 1000mm - Twilight Blue
87016 Old London Floor Standing 2 Door Vanity Unit with 1 Tap Hole White Marble Top 1000mm - Twilight Blue
87017 Old London Floor Standing 2 Door Vanity Unit with 3 Tap Hole Grey Marble Top 1000mm - Twilight Blue
87020 Old London Floor Standing 4 Door Angled Vanity Unit with 1 Tap Hole Grey Marble Top 100mm - Twilight Blue
87021 Old London Floor Standing 4 Door Angled Vanity Unit with 3 Tap Hole Black Marble Top 1000mm - Twilight Blue
87022 Old London Floor Standing 4 Door Angled Vanity Unit with 3 Tap Hole White Marble Top 1000mm - Twilight Blue
87023 Old London Floor Standing 4 Door Angled Vanity Unit with 3 Tap Hole Grey Marble Top 1000mm - Twilight Blue
87079 Old London Floor Standing 4 Door Angled Vanity Unit with 1 Tap Hole Black Marble Top 1000mm - Timeless Sand
87080 Old London Floor Standing 4 Door Angled Vanity Unit with 1 Tap Hole White Marble Top 1000mm - Timeless Sand
87081 Old London Floor Standing 4 Door Angled Vanity Unit with 1 Tap Hole Grey Marble Top 1000mm - Timeless Sand
87082 Old London Floor Standing 4 Door Angled Vanity Unit with 3 Tap Hole Black Marble Top 1000mm - Timeless Sand
87083 Old London Floor Standing 4 Door Angled Vanity Unit with 3 Tap Hole White Marble Top 1000mm - Timeless Sand
87084 Old London Floor Standing 4 Door Angled Vanity Unit with 3 Tap Hole Grey Marble Top 1000mm - Timeless Sand
87130 Old London Floor Standing Angled 4 Door Vanity Unit with 1 Tap Hole Black Marble Top 1000mm - Hunter Green
87131 Old London Floor Standing Angled 4 Door Vanity Unit with 1 Tap Hole Grey Marble Top 1000mm - Hunter Green
87132 Old London Floor Standing Angled 4 Door Vanity Unit with 1 Tap Hole White Marble Top 1000mm - Hunter Green
87133 Old London Floor Standing Angled 4 Door Vanity Unit with 3 Tap Hole Black Marble Top 1000mm - Hunter Green
87134 Old London Floor Standing Angled 4 Door Vanity Unit with 3 Tap Hole Grey Marble Top 1000mm - Hunter Green
87135 Old London Floor Standing Angled 4 Door Vanity Unit with 3 Tap Hole White Marble Top 1000mm - Hunter Green