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 (
    89734, 91286, 82415, 86854, 89339, 82355, 
    90093, 90103, 90112, 89438, 82398, 
    86849, 89730, 91293, 89353, 82380, 
    89333, 89354, 82340, 82341, 82346, 
    86389, 86391, 89430, 83115, 83125, 
    83134, 82449, 86823, 89123, 89127, 
    89159, 89550, 89355, 89356, 83087, 
    89284, 89437, 91289, 84262, 84266, 
    90120, 89157, 89548, 90092, 90102, 
    90111, 89335
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00099

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 (89734,91286,82415,86854,89339,82355,90093,90103,90112,89438,82398,86849,89730,91293,89353,82380,89333,89354,82340,82341,82346,86389,86391,89430,83115,83125,83134,82449,86823,89123,89127,89159,89550,89355,89356,83087,89284,89437,91289,84262,84266,90120,89157,89548,90092,90102,90111,89335)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
82340 nuie Edwardian Triple Thermostatic Shower Valve - Chrome
82341 nuie Edwardian Triple Thermostatic Shower Valve - Chrome
82346 nuie Victorian Triple Thermostatic Shower Valve - Chrome
82355 nuie Shower Kits Traditional Thermostatic Shower Valve & Kit - Chrome / White
82380 Hudson Reed Multi Option Shower Kits Round Brass Thermostatic Bar Valve & Shower Kit - Chrome
82398 Hudson Reed Tec Pura Twin Thermostatic Shower Valve With Diverter - Matt Black
82415 Hudson Reed Tec Pura Twin Thermostatic Shower Valve - Brushed Brass
82449 nuie Shower Kits Rigid Riser Kit - Chrome
83087 Hudson Reed Art Triple Thermostatic Shower Valve - Chrome
83115 nuie Arvan Triple Thermostatic Valve With Diverter - Matt Black
83125 nuie Arvan Triple Thermostatic Valve With Diverter - Gunmetal
83134 nuie Arvan Triple Thermostatic Valve With Diverter - Brushed Brass
84262 Old London Black Topaz Twin Concealed Shower Valve - Chrome / Black
84266 Old London Black Topaz Twin Exposed Shower Valve - Chrome / Black
86389 nuie Victorian Triple Thermostatic Shower Valve - Chrome
86391 nuie Victorian Triple Thermostatic Shower Valve - Chrome
86823 nuie Shower Kits Square Thermostatic Bar Valve & Shower Kit - Brushed Brass
86849 Hudson Reed Tec Crosshead Twin Thermostatic Shower Valve With Diverter - Matt Black
86854 Hudson Reed Tec Crosshead Twin Thermostatic Shower Valve - Brushed Brass
89123 Hudson Reed Reign Triple Thermostatic Shower Valve - Chrome
89127 Hudson Reed Reign Triple Thermostatic Shower Valve - Chrome
89157 Hudson Reed Indus Twin Thermostatic Shower Valve With Diverter - Chrome
89159 Hudson Reed Round Valves Triple Valve - Chrome
89284 nuie 1 Outlet Bundle Arvan - Chrome
89333 nuie Windon Thermostatic Square Bath Shower Mixer & Single Function Slide Rail Shower Kit - Chrome
89335 nuie Sanford Thermostatic Square Bath Shower Mixer & Single Function Slide Rail Shower Kit - Chrome
89339 nuie 1 Outlet Bundle Windon - Chrome
89353 nuie Windon Thermostatic Concealed Twin Square Valve & Slide Rail Kit with Single Function Handset & Outlet Elbow Shower Kit - Chrome
89354 nuie Windon Thermostatic Concealed Twin Square Valve, Wall Mount Shower Arm & Square Fixed Head Shower Kit - Chrome
89355 nuie Sanford Thermostatic Concealed Twin Square Valve & Slide Rail Kit with Single Function Handset & Outlet Elbow Shower Kit - Chrome
89356 nuie Sanford Thermostatic Concealed Twin Square Valve, Wall Mount Shower Arm & Square Fixed Head Shower Kit - Chrome
89430 Hudson Reed Industrial Valves Triple Valve - Chrome
89437 Hudson Reed Industrial Valves Twin Valve with Diverter - Chrome
89438 Hudson Reed Industrial Valves Twin Valve - Matt Black
89548 Hudson Reed Lennox Twin Thermostatic Shower Valve With Diverter - Chrome
89550 Hudson Reed Square Valves Triple Valve - Chrome
89730 Old London White Topaz Twin Concealed Shower Valve with Diverter - Chrome / White
89734 Old London White Topaz Triple Thermostatic Shower Valve - Chrome / White
90092 nuie Windon Triple Thermostatic Valve - Matt Black
90093 nuie Windon Triple Thermostatic Valve With Diverter - Matt Black
90102 nuie Windon Triple Thermostatic Valve - Gunmetal
90103 nuie Windon Triple Thermostatic Valve With Diverter - Gunmetal
90111 nuie Windon Triple Thermostatic Valve - Brushed Brass
90112 nuie Windon Triple Thermostatic Valve With Diverter - Brushed Brass
90120 nuie Windon Triple Thermostatic Valve With Diverter - Chrome
91286 nuie Aztec Triple Thermostatic Concealed Shower Valve with Diverter - 3 Outlet - Matt Black
91289 nuie Aztec Triple Thermostatic Concealed Shower Valve - 2 Outlet - Matt Black
91293 nuie Aztec Triple Thermostatic Concealed Shower Valve - 2 Outlet - Brushed Brass