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 (
    91246, 91248, 91249, 91250, 89755, 89757, 
    86187, 86210, 86511, 86787, 84681, 
    84682, 84685, 84686, 91076, 91077, 
    91080, 91081, 91083, 91084, 91085, 
    86902, 86927, 86963, 86988, 87024, 
    87049, 87085, 87107, 91131
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00081

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "13.52"
    },
    "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": 30,
      "rows_produced_per_join": 30,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "10.52",
        "eval_cost": "3.00",
        "prefix_cost": "13.52",
        "data_read_per_join": "114K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (91246,91248,91249,91250,89755,89757,86187,86210,86511,86787,84681,84682,84685,84686,91076,91077,91080,91081,91083,91084,91085,86902,86927,86963,86988,87024,87049,87085,87107,91131)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
84681 Hudson Reed Fusion Floor Standing 2 Door Vanity Unit & WC with Left Hand Semi Recessed Basin Combination 1100mm - Gloss Grey
84682 Hudson Reed Fusion Floor Standing 2 Door Vanity Unit & WC with Right Hand Semi Recessed Basin Combination 1100mm - Gloss Grey
84685 Hudson Reed Fusion Floor Standing 2 Door Vanity Unit & WC with Left Hand Semi Recessed Basin Combination 1100mm - Gloss Grey
84686 Hudson Reed Fusion Floor Standing 2 Door Vanity Unit & WC with Right Hand Semi Recessed Basin Combination 1100mm - Gloss Grey
86187 Hudson Reed Havana Wall Hung 4 Drawer Unit & Colour Match Worktop, 1200mm - Metallic Slate
86210 Hudson Reed Havana Wall Hung 4 Drawer Unit & Colour Match Worktop, 1200mm - Autumn Oak
86511 Hudson Reed Juno 1200mm Wall Hung 4-Drawer Vanity & Worktop - Autumn Oak
86787 Hudson Reed Juno Wall Hung 4 Drawer Vanity Unit & Colour Match Worktop, 1200mm - Metallic Slate
86902 Old London Floor Standing 2 Door Vanity Unit with 1 Tap Hole Ceramic Basin 600mm - Storm Grey
86927 Old London Floor Standing 2 Door Vanity Unit with 3 Tap Hole Ceramic Basin 600mm - Storm Grey
86963 Old London Floor Standing 2 Door Vanity Unit with 1 Tap Hole Ceramic Basin 600mm - Twilight Blue
86988 Old London Floor Standing 2 Door Vanity Unit with 3 Tap Hole Ceramic Basin 600mm - Twilight Blue
87024 Old London Floor Standing 2 Door Vanity Unit with 1 Tap Hole Ceramic Basin 600mm - Timeless Sand
87049 Old London Floor Standing 2 Door Vanity Unit with 3 Tap Hole Ceramic Basin 600mm - Timeless Sand
87085 Old London Floor Standing 2 Door Vanity Unit with 1 Tap Hole Ceramic Basin 600mm - Hunter Green
87107 Old London Floor Standing 2 Door Vanity Unit with 3 Tap Hole Ceramic Basin 600mm - Hunter Green
89755 Hudson Reed Urban 1200mm Wall Hung 4-Drawer Vanity & Double Polymarble Basin - Satin White
89757 Hudson Reed Urban 1200mm Wall Hung 4-Drawer Vanity & Double Ceramic Basin - Satin White
91076 nuie Classique Floor Standing 2 Door Unit & 1 Tap Hole Marble Top with Oval Basin, 800mm - Satin White/Black
91077 nuie Classique Floor Standing 2 Door Unit & 3 Tap Hole Marble Top with Oval Basin, 800mm - Satin White/Black
91080 nuie Classique Floor Standing 2 Door Unit & 1 Tap Hole Marble Top with Oval Basin, 800mm - Satin White/Grey
91081 nuie Classique Floor Standing 2 Door Unit & 3 Tap Hole Marble Top with Oval Basin, 800mm - Satin White/Grey
91083 nuie Classique Floor Standing 2 Door Unit & 1 Tap Hole Marble Top with Oval Basin, 800mm - Satin White/White
91084 nuie Classique Floor Standing 2 Door Unit & 3 Tap Hole Marble Top with Oval Basin, 800mm - Satin White/White
91085 nuie Classique Floor Standing 2 Door Unit & 1 Tap Hole Marble Top with Square Basin, 800mm - Satin White/White
91131 nuie Classique Wall Hung 1 Drawer Unit & 1 Tap Hole Marble Top with Oval Basin, 800mm - Satin Anthracite/Black
91246 nuie Classique Floor Standing 2 Door Unit & 3 Tap Hole Marble Top with Oval Basin, 800mm - Satin Green/Grey
91248 nuie Classique Floor Standing 2 Door Unit & 1 Tap Hole Marble Top with Oval Basin, 800mm - Satin Green/White
91249 nuie Classique Floor Standing 2 Door Unit & 3 Tap Hole Marble Top with Oval Basin, 800mm - Satin Green/White
91250 nuie Classique Floor Standing 2 Door Unit & 1 Tap Hole Marble Top with Square Basin, 800mm - Satin Green/White