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 (
    85645, 87388, 88390, 91428, 91430, 82560, 
    82565, 82569, 82573, 85570, 82562, 
    82566, 82570, 84243, 86361, 86367, 
    87785, 87790, 87796, 88395, 88585, 
    90266, 90273, 91968
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00083

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "12.97"
    },
    "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": 24,
      "rows_produced_per_join": 24,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "10.57",
        "eval_cost": "2.40",
        "prefix_cost": "12.97",
        "data_read_per_join": "91K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (85645,87388,88390,91428,91430,82560,82565,82569,82573,85570,82562,82566,82570,84243,86361,86367,87785,87790,87796,88395,88585,90266,90273,91968)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
82560 nuie Square Wall Mounted Shower Arm - Chrome
82562 Hudson Reed Fixed Shower Heads Wall-Mounted Arm - Matt Black
82565 Hudson Reed Fixed Shower Heads Ceiling-Mounted Arm - Matt Black
82566 nuie Fixed Shower Heads Wall Hung Shower Arm - Gunmetal
82569 nuie Fixed Shower Heads Round Ceiling Arm 300mm - Gunmetal
82570 Hudson Reed Fixed Shower Heads Wall-Mounted Arm - Brushed Brass
82573 Hudson Reed Fixed Shower Heads Ceiling-Mounted Arm - Brushed Brass
84243 nuie Athena Straight End Panel & Plinth 750mm - White
85570 Traditional Basin Black Pull Up Waste
85645 Hudson Reed Wastes & Extras Cistern Cut-Off Valve - Chrome
86361 nuie Heating Accessories Angled Radiator Valve Pack (Pairs) - Chrome
86367 nuie Heating Accessories Straight Radiator Valve Pack (Pairs) - Chrome
87388 nuie Ceramics Accessories Round Flush Plate for Pneumatic Dual Flush - Brushed Brass
87785 nuie Athena Furniture Worktop 500mm - Gloss Grey
87790 nuie Athena Furniture Worktop 600mm - Anthracite Woodgrain
87796 nuie Athena Furniture Worktop 600mm - Hacienda Black
88390 nuie Toilet Seats Luxury Top Fix Soft Close Toilet Seat - White
88395 Hudson Reed Toilet Seats Traditional Toilet Seat Plastic Hinges - White
88585 Hudson Reed Fusion Bath End Panel & Plinth 750mm - Gloss White
90266 Hudson Reed Wetroom Wall Channel 1950mm Black - Matt Black
90273 Hudson Reed Wetroom Wall Channel 1950mm Brass - Brushed Brass
91428 nuie Toilet Seats Round Wrapover Soft Close Top Fix Toilet Seat - For use with Freya Toilets - White
91430 nuie Toilet Seats Square Wrapover Soft Close Top Fix Toilet Seat - For use with Ava Toilets - White
91968 BC Designs Victrion Ceiling Mounted Shower Arm - Chrome