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 (
    91846, 91847, 86891, 91868, 91849, 91850, 
    91851, 91852, 91853, 91854, 91855, 
    91857, 91858, 91859, 91860, 91861, 
    91862, 91863, 92227, 82402, 92210, 
    85577, 92373, 92383, 92384, 92385, 
    92386, 92387, 92388, 92389, 91889, 
    91890, 91891, 92333, 92334, 92335, 
    92336, 86888, 92365, 86890, 91864, 
    92374, 85576, 85584, 85572, 86900, 
    85592, 85546
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00128

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 (91846,91847,86891,91868,91849,91850,91851,91852,91853,91854,91855,91857,91858,91859,91860,91861,91862,91863,92227,82402,92210,85577,92373,92383,92384,92385,92386,92387,92388,92389,91889,91890,91891,92333,92334,92335,92336,86888,92365,86890,91864,92374,85576,85584,85572,86900,85592,85546)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
82402 Large Traditional Handset Black
85546 Traditional Basin Pull Up Waste
85572 Black Ceramic Handle WC Lever
85576 Extended Retainer Bath Waste & Overflow
85577 nuie Wastes & Extras Pop Up Bath Waste - Chrome
85584 Classic Concealed Bath Waste & Overflow
85592 Square Sprung Plug Bath Waste
86888 Traditional Toilet Roll Holder
86890 Traditional Soap Dish
86891 Traditional Gallery Shelf
86900 Wirework Deep Corner Basket
91846 BC Designs Victrion Dog Bone Toilet Roll Holder with Back Plate - Gold
91847 BC Designs Victrion Dog Bone Toilet Roll Holder with Back Plate - Nickel
91849 BC Designs Victrion Classic Rounded Towel Ring - Brushed Chrome
91850 BC Designs Victrion Classic Rounded Towel Ring - Brushed Copper
91851 BC Designs Victrion Classic Rounded Towel Ring - Brushed Gold
91852 BC Designs Victrion Classic Rounded Towel Ring - Brushed Nickel
91853 BC Designs Victrion Classic Rounded Towel Ring - Copper
91854 BC Designs Victrion Classic Rounded Towel Ring - Gold
91855 BC Designs Victrion Classic Rounded Towel Ring - Nickel
91857 BC Designs Victrion Ceramic Soap Dish Holder - Brushed Chrome
91858 BC Designs Victrion Ceramic Soap Dish Holder - Brushed Copper
91859 BC Designs Victrion Ceramic Soap Dish Holder - Brushed Gold
91860 BC Designs Victrion Ceramic Soap Dish Holder - Brushed Nickel
91861 BC Designs Victrion Ceramic Soap Dish Holder - Copper
91862 BC Designs Victrion Ceramic Soap Dish Holder - Gold
91863 BC Designs Victrion Ceramic Soap Dish Holder - Nickel
91864 BC Designs Victrion Glass Gallery Shelf - Chrome
91868 BC Designs Victrion Double Towel Rail - Chrome
91889 BC Designs Victrion Open Toilet Roll Holder - Copper
91890 BC Designs Victrion Open Toilet Roll Holder - Gold
91891 BC Designs Victrion Open Toilet Roll Holder - Nickel
92210 BC Designs Bath Wastes Push Down Bath Waste 70mm (Slotted) - Chrome
92227 BC Designs Bath Wastes Push Down Bath Waste 60mm (Unslotted) - Chrome
92333 BC Designs Victrion Toilet Roll Holder - Brushed Chrome
92334 BC Designs Victrion Toilet Roll Holder - Brushed Copper
92335 BC Designs Victrion Toilet Roll Holder - Brushed Gold
92336 BC Designs Victrion Toilet Roll Holder - Brushed Nickel
92365 BC Designs Basin Bottle Trap - Chrome
92373 BC Designs Waste Trap For Furniture Basins - White
92374 BC Designs Waste Trap For Furniture Basins - White
92383 BC Designs Lever Handle for Close Coupled/Low Level Cistern - Brushed Chrome/White
92384 BC Designs Lever Handle for Close Coupled/Low Level Cistern - Brushed Copper/White
92385 BC Designs Lever Handle for Close Coupled/Low Level Cistern - Brushed Gold/White
92386 BC Designs Lever Handle for Close Coupled/Low Level Cistern - Brushed Nickel/White
92387 BC Designs Lever Handle for Close Coupled/Low Level Cistern - Copper/White
92388 BC Designs Lever Handle for Close Coupled/Low Level Cistern - Gold/White
92389 BC Designs Lever Handle for Close Coupled/Low Level Cistern - Nickel/White