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 (
    91863, 92227, 82402, 88146, 88589, 89589, 
    92210, 87786, 87874, 85554, 85577, 
    87792, 87798, 87880, 86366, 86368, 
    86806, 92373, 91900, 87873, 90317, 
    90319, 90320, 84244
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00066

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 (91863,92227,82402,88146,88589,89589,92210,87786,87874,85554,85577,87792,87798,87880,86366,86368,86806,92373,91900,87873,90317,90319,90320,84244)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
82402 Large Traditional Handset Black
84244 Athena End Panel & Plinth 800mm - Gloss White
85554 Waste Trap For Furniture Basins
85577 nuie Wastes & Extras Pop Up Bath Waste - Chrome
86366 nuie Heating Accessories Crosshead Angled Radiator Valve Pack (Pairs) - Chrome
86368 nuie Heating Accessories Crosshead Straight Radiator Valve Pack (Pairs) - Chrome
86806 nuie Shower Kits Slide Rail Kit - Chrome
87786 nuie Athena Furniture Worktop 600mm - Gloss Grey
87792 nuie Athena Furniture Worktop 800mm - Anthracite Woodgrain
87798 nuie Athena Furniture Worktop 800mm - Hacienda Black
87873 nuie Mayford Round Ceramic 1 Tap Hole Basin 450mm
87874 nuie Mayford Round Ceramic 1 Tap Hole Basin 550mm
87880 nuie Mayford Square Ceramic 1 Tap Hole Basin 450mm
88146 nuie Athena Shower Bath End Panel 700mm - Gloss White
88589 Hudson Reed Fusion Shower Bath End Panel 700mm - Gloss White
89589 nuie Shower Kits Slide Rail Kit - Chrome
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
91863 BC Designs Victrion Ceramic Soap Dish Holder - Nickel
91900 BC Designs Victrion Double Corner Shower Basket - Chrome
92210 BC Designs Bath Wastes Push Down Bath Waste 70mm (Slotted) - Chrome
92227 BC Designs Bath Wastes Push Down Bath Waste 60mm (Unslotted) - Chrome
92373 BC Designs Waste Trap For Furniture Basins - White