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 (
    86508, 86509, 86784, 86785, 82855, 82856, 
    82928, 82929, 83001, 83002, 83517, 
    83518, 83525, 83526, 85366, 85367, 
    86146, 86169, 86662, 86731, 89071, 
    89072, 82600, 83076
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00075

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 (86508,86509,86784,86785,82855,82856,82928,82929,83001,83002,83517,83518,83525,83526,85366,85367,86146,86169,86662,86731,89071,89072,82600,83076)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
82600 nuie Arno 1200mm Wall Hung 2-Drawer Vanity & Worktop - Gloss White
82855 nuie Arno 800mm Wall Hung 2-Drawer Vanity & Laminate Top - Solace Oak
82856 nuie Arno 800mm Wall Hung 2-Drawer Vanity & Laminate Top - Solace Oak
82928 nuie Arno 800mm Wall Hung 2-Drawer Vanity & Laminate Top - Anthracite
82929 nuie Arno 800mm Wall Hung 2-Drawer Vanity & Laminate Top - Anthracite
83001 nuie Arno 800mm Wall Hung 2-Drawer Vanity & Laminate Top - Charcoal Black
83002 nuie Arno 800mm Wall Hung 2-Drawer Vanity & Laminate Top - Charcoal Black
83076 nuie Arno 800mm Wall Hung 2-Drawer Vanity & Worktop - Satin Green
83517 nuie Athena Wall Hung 2 Drawer Vanity With Sparkling Black Worktop 800mm - Anthracite Woodgrain
83518 nuie Athena Wall Hung 2 Drawer Vanity With Sparkling White Worktop 800mm - Anthracite Woodgrain
83525 nuie Athena Wall Hung 2 Drawer Vanity With Sparkling Black Worktop 800mm - Hacienda Black
83526 nuie Athena Wall Hung 2 Drawer Vanity With Sparkling White Worktop 800mm - Hacienda Black
85366 nuie Deco 800mm Wall Hung 2-Drawer Vanity & Laminate Top - Satin White
85367 nuie Deco 800mm Wall Hung 2-Drawer Vanity & Laminate Top - Satin White
86146 Hudson Reed Havana Wall Hung 2 Drawer Unit & Laminate Worktop, 800mm - Graphite Grey/Bellato Grey
86169 Hudson Reed Havana Wall Hung 2 Drawer Unit & Laminate Worktop, 800mm - Coastal Grey/Bellato Grey
86508 Hudson Reed Juno 600mm Wall Hung 2-Drawer Vanity & Laminate Top - Autumn Oak
86509 Hudson Reed Juno 600mm Wall Hung 2-Drawer Vanity & Laminate Top - Autumn Oak
86662 Hudson Reed Juno 800mm Wall Hung 2-Drawer Vanity & Laminate Top - Graphite Grey
86731 Hudson Reed Juno 800mm Wall Hung 2-Drawer Vanity & Laminate Top - Coastal Grey
86784 Hudson Reed Juno Wall Hung 2 Drawer Vanity Unit & Laminate Worktop, 600mm - Metallic Slate/Sparkle Black
86785 Hudson Reed Juno Wall Hung 2 Drawer Vanity Unit & Laminate Worktop, 600mm - Metallic Slate/Sparkle White
89071 Hudson Reed Quartet Wall Hung 2 Drawer Cabinet with Sparkling Black Worktop 720mm - Gloss White
89072 Hudson Reed Quartet Wall Hung 2 Drawer Cabinet with Sparkling White Worktop 720mm - Gloss White