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 (
    82818, 82891, 82964, 83338, 83348, 84880, 
    84895, 87399, 82588, 82589, 84869, 
    84538, 84604, 89212, 89225, 89238, 
    90005, 82826, 82899, 82972, 84868, 
    85666, 85686, 85698
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00067

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "10.82"
    },
    "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": "8.42",
        "eval_cost": "2.40",
        "prefix_cost": "10.82",
        "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 (82818,82891,82964,83338,83348,84880,84895,87399,82588,82589,84869,84538,84604,89212,89225,89238,90005,82826,82899,82972,84868,85666,85686,85698)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
82588 nuie Arno 500mm Wall Hung 2-Door Vanity & Thin-Edge Basin - Gloss White
82589 nuie Arno 500mm Wall Hung 2-Door Vanity & Curved Basin - Gloss White
82818 nuie Arno 600mm Wall Hung 1-Drawer Vanity & Worktop - Solace Oak
82826 nuie Arno 600mm Wall Hung 2-Door Vanity & Laminate Top - Solace Oak
82891 nuie Arno 600mm Wall Hung 1-Drawer Vanity & Worktop - Anthracite
82899 nuie Arno 600mm Wall Hung 2-Door Vanity & Laminate Top - Anthracite
82964 nuie Arno 600mm Wall Hung 1-Drawer Vanity & Worktop - Charcoal Black
82972 nuie Arno 600mm Wall Hung 2-Door Vanity & Laminate Top - Charcoal Black
83338 nuie Athena Wall Hung Single Drawer Vanity With Worktop 600mm - Anthracite Woodgrain
83348 nuie Athena Wall Hung Single Drawer Vanity With Worktop 600mm - Hacienda Black
84538 Hudson Reed Fusion Wall Hung 1 Door Vanity Unit & Polymarble Basin Compact 400mm - Anthracite Woodgrain
84604 Hudson Reed Fusion Wall Hung 1 Door Vanity Unit & Polymarble Basin Compact 400mm - Hacienda Black
84868 nuie Core Floor Standing Single Door Vanity With Ceramic Basin 400mm - Gloss White
84869 nuie Core Wall Hung 2 Door Vanity With Ceramic Basin 500mm - Gloss White
84880 nuie Core Floor Standing 1 Door Vanity Basin Unit & Ceramic Basin, 400mm - Satin Anthracite
84895 nuie Core Floor Standing 1 Door Vanity Basin Unit & Ceramic Basin, 400mm - Satin Green
85666 nuie Deco 400mm Wall Hung Tall Unit - Satin Anthracite
85686 nuie Deco 400mm Wall Hung Tall Unit - Satin Grey
85698 nuie Deco 400mm Wall Hung Tall Unit - Satin Blue
87399 nuie Merit Wall Hung Slimline Single Door Vanity and Ceramic Basin 500mm - Gloss White
89212 Hudson Reed Sarenna Floor Standing WC Unit 550mm - Moon White
89225 Hudson Reed Sarenna Floor Standing WC Unit 550mm - Dove Grey
89238 Hudson Reed Sarenna Floor Standing WC Unit 550mm - Mineral Blue
90005 nuie Mayford Wall Hung 2 Door Vanity Unit with Ceramic Basin 450mm - Gloss White