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 (
    90000, 82618, 83421, 89833, 89885, 89957, 
    91523, 86475, 86476, 86624, 86625, 
    86693, 86694, 86751, 86752, 85351, 
    86519, 86795, 83046, 83047, 90882, 
    90883, 90961, 90962
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00050

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 (90000,82618,83421,89833,89885,89957,91523,86475,86476,86624,86625,86693,86694,86751,86752,85351,86519,86795,83046,83047,90882,90883,90961,90962)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
82618 nuie Arno 600mm Wall Hung 2-Drawer Vanity & Laminate Top - Gloss White
83046 nuie Arno 600mm Wall Hung 2-Door Vanity & Laminate Top - Satin Green
83047 nuie Arno 600mm Wall Hung 2-Door Vanity & Laminate Top - Satin Green
83421 nuie Athena Wall Hung 2 Drawer Vanity With Grey Worktop 600mm - Gloss White
85351 nuie Deco 600mm Wall Hung Single Drawer Vanity & Minimalist Basin - Satin White
86475 Hudson Reed Juno 500mm Wall Hung 2-Door Vanity & Thin-Edge 1 Tap Hole Basin - Autumn Oak
86476 Hudson Reed Juno 500mm Wall Hung 2-Door Vanity & Curved 1 Tap Hole Basin - Autumn Oak
86519 Hudson Reed Juno 800mm Wall Hung Single Drawer Vanity & Worktop - Autumn Oak
86624 Hudson Reed Juno 600mm Wall Hung Single Drawer Vanity & Laminate Top - Graphite Grey
86625 Hudson Reed Juno 600mm Wall Hung Single Drawer Vanity & Laminate Top - Graphite Grey
86693 Hudson Reed Juno 600mm Wall Hung Single Drawer Vanity & Laminate Top - Coastal Grey
86694 Hudson Reed Juno 600mm Wall Hung Single Drawer Vanity & Laminate Top - Coastal Grey
86751 Hudson Reed Juno Wall Hung 2 Door Vanity Basin Unit & Thin-Edge Ceramic Basin, 500mm - Metallic Slate
86752 Hudson Reed Juno Wall Hung 2 Door Vanity Basin Unit & Curved Ceramic Basin, 500mm - Metallic Slate
86795 Hudson Reed Juno Wall Hung 1 Drawer Vanity Unit & Colour Match Worktop, 800mm - Metallic Slate
89833 Hudson Reed Urban Floor Standing 2 Door Vanity Unit with Minimalist Basin 600mm - Satin Grey
89885 Hudson Reed Urban Floor Standing 2 Door Vanity Unit with Minimalist Basin 600mm - Satin Blue
89957 Hudson Reed Urban 600mm Floor Standing 2-Door Unit and Minimalist Basin 1 Tap Hole - Satin Green
90000 nuie Eden Floor Standing 2 Door Vanity Unit with Minimalist Basin 600mm - Gloss White
90882 nuie Arno Wall Hung 2 Door Vanity & Laminate Worktop, 600mm - Satin Anthracite/Sparkle Black
90883 nuie Arno Wall Hung 2 Door Vanity & Laminate Worktop, 600mm - Satin Anthracite/Sparkle White
90961 nuie Arno Wall Hung 2 Door Vanity & Laminate Worktop, 600mm - Satin Grey/Sparkle Black
90962 nuie Arno Wall Hung 2 Door Vanity & Laminate Worktop, 600mm - Satin Grey/Sparkle White
91523 Hudson Reed Urban Floor Standing 2 Door Vanity & Minimalist Ceramic Basin, 600mm - Satin Anthracite