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 (
    87994, 90317, 90319, 90320, 85645, 87388, 
    88390, 91428, 91430, 88395, 86887, 
    85581, 88389, 88391, 88388, 88095, 
    88392, 92408, 87993, 91427, 91429, 
    87387, 87389, 87383, 87384, 87385, 
    89612, 89613, 88393, 87386, 87382, 
    89611, 82328, 88860, 88861, 88862, 
    88863, 88864, 90819, 90820, 90821, 
    90822, 85563, 88929, 82434, 88858, 
    88859, 90817
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00101

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "21.63"
    },
    "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": 48,
      "rows_produced_per_join": 48,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "16.83",
        "eval_cost": "4.80",
        "prefix_cost": "21.63",
        "data_read_per_join": "183K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (87994,90317,90319,90320,85645,87388,88390,91428,91430,88395,86887,85581,88389,88391,88388,88095,88392,92408,87993,91427,91429,87387,87389,87383,87384,87385,89612,89613,88393,87386,87382,89611,82328,88860,88861,88862,88863,88864,90819,90820,90821,90822,85563,88929,82434,88858,88859,90817)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
82328 nuie Shelf Support Brackets - Dark Grey
82434 nuie Ceramics Accessories Basin Fixing Bolts (Pair)
85563 nuie Ceramics Accessories Metal Universal Lever - Chrome
85581 Basin Bottle Trap
85645 Hudson Reed Wastes & Extras Cistern Cut-Off Valve - Chrome
86887 nuie Legend Soft Close Wooden Toilet Seat - White
87382 nuie Ceramics Accessories Square Dual Flush Chrome Push Button -
87383 nuie Ceramics Accessories Square Dual Flush Black Push Button -
87384 nuie Ceramics Accessories Square Dual Flush Brushed Brass Push Button -
87385 nuie Square Dual Flush Push Button - Gun Metal
87386 nuie Ceramics Accessories Round Flush Plate for Pneumatic Dual Flush - Chrome
87387 nuie Ceramics Accessories Round Flush Plate for Pneumatic Dual Flush - Matt Black
87388 nuie Ceramics Accessories Round Flush Plate for Pneumatic Dual Flush - Brushed Brass
87389 nuie Ceramics Accessories Round Flush Plate for Pneumatic Dual Flush - Matt White
87993 nuie Toilet Seats Square Top Fix Soft Close Toilet Seat - White
87994 nuie Toilet Seats Luxury Square Top Fix Soft Close Toilet Seat - White
88095 Old London Richmond Towel Rail - Chrome
88388 nuie Toilet Seats D Shaped Top Fix Soft Close Toilet Seat - White
88389 nuie Toilet Seats Luxury Top Fix Soft Close Toilet Seat - White
88390 nuie Toilet Seats Luxury Top Fix Soft Close Toilet Seat - White
88391 nuie Toilet Seats Luxury D Shaped Top Fix Soft Close Toilet Seat - White
88392 nuie Toilet Seats Standard Top Fix Soft Close Toilet Seat - White
88393 nuie Toilet Seats Soft Close Bottom Fix Toilet Seat - White
88395 Hudson Reed Toilet Seats Traditional Toilet Seat Plastic Hinges - White
88858 nuie Ceramics Accessories Overflow Cover - Chrome
88859 nuie Carlton Overflow Cover - Chrome
88860 nuie Ceramics Accessories Overflow Cover - Matt Black
88861 nuie Carlton Overflow Cover - Black
88862 nuie Ceramics Accessories Overflow Cover - Brushed Brass
88863 nuie Carlton Overflow Cover - Brushed Brass
88864 nuie Wastes & Extras Basin Overflow Cover - Gunmetal
88929 nuie Ceramics Accessories Pan Fixing Kit
89611 nuie Ceramics Accessories Dual Flush Button - Chrome
89612 nuie Ceramics Accessories Dual Flush Button - Black
89613 nuie Ceramics Accessories Dual Flush Button - Brushed Brass
90317 nuie Ceramics Accessories Dual Flush Concealed Cistern
90319 nuie Ceramics Accessories Dual Flush Concealed Cistern - Chrome
90320 nuie Ceramics Accessories Dual Flush Concealed Cistern - Chrome
90817 Hudson Reed Chancery Chrome Overflow Cover
90819 Hudson Reed Chancery Black Overflow Cover
90820 Oval Matt Black Overflow Cover - Matt Black
90821 Hudson Reed Chancery Brushed Brass Overflow Cover
90822 Oval Brushed Brass Overflow Cover - Brushed Brass
91427 nuie Toilet Seats Round Soft Close Sandwich Top Fix Toilet Seat - For use with Freya Toilets - White
91428 nuie Toilet Seats Round Wrapover Soft Close Top Fix Toilet Seat - For use with Freya Toilets - White
91429 nuie Toilet Seats Square Wrapover Soft Close Top Fix Toilet Seat - For use with Ava Toilets - White
91430 nuie Toilet Seats Square Wrapover Soft Close Top Fix Toilet Seat - For use with Ava Toilets - White
92408 BC Designs Towel Rail for Ornate Basin Stand - Chrome