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 (
    84605, 87392, 87393, 82821, 82894, 82967, 
    82807, 82808, 82880, 82881, 82953, 
    82954, 84343, 84344, 84643, 85356, 
    88178, 90809, 83196, 83197, 84627, 
    89996, 85724, 85741
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00077

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 (84605,87392,87393,82821,82894,82967,82807,82808,82880,82881,82953,82954,84343,84344,84643,85356,88178,90809,83196,83197,84627,89996,85724,85741)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
82807 nuie Arno 500mm Wall Hung 2-Door Vanity & Thin-Edge Basin - Solace Oak
82808 nuie Arno 500mm Wall Hung 2-Door Vanity & Curved Basin - Solace Oak
82821 nuie Arno 600mm Wall Hung 2-Door Vanity & Minimalist Basin - Solace Oak
82880 nuie Arno 500mm Wall Hung 2-Door Vanity & Thin-Edge Basin - Anthracite
82881 nuie Arno 500mm Wall Hung 2-Door Vanity & Curved Basin - Anthracite
82894 nuie Arno 600mm Wall Hung 2-Door Vanity & Minimalist Basin - Anthracite
82953 nuie Arno 500mm Wall Hung 2-Door Vanity & Thin-Edge Basin - Charcoal Black
82954 nuie Arno 500mm Wall Hung 2-Door Vanity & Curved Basin - Charcoal Black
82967 nuie Arno 600mm Wall Hung 2-Door Vanity & Minimalist Basin - Charcoal Black
83196 nuie Athena Wall Hung Single Drawer Vanity With Thin-Edge 1 Tap Hole Ceramic Basin 500mm - Gloss White
83197 nuie Athena Wall Hung Single Drawer Vanity With Curved 1 Tap Hole Ceramic Basin 500mm - Gloss White
84343 Hudson Reed Fusion Wall Hung 2 Door Vanity Unit & Polymarble Basin 500mm - Gloss White
84344 Hudson Reed Fusion Wall Hung 2 Door Vanity Unit & Ceramic Basin 500mm - Gloss White
84605 Hudson Reed Fusion Wall Hung 2 Door Vanity Unit & Polymarble Basin Compact 500mm - Hacienda Black
84627 Hudson Reed Fusion Floor Standing WC Unit with Coordinating Top 500mm - Gloss Grey
84643 Hudson Reed Fusion Floor Standing WC Unit with Coordinating Top Compact 600mm - Gloss Grey
85356 nuie Deco 600mm Wall Hung Single Drawer Vanity & Laminate Top - Satin White
85724 Hudson Reed Fluted 400mm Tall Unit Single Door - Satin Anthracite
85741 Hudson Reed Fluted 400mm Tall Unit Single Door - Satin Grey
87392 nuie Merit Wall Hung Single Door Vanity and Ceramic Basin 500mm - Anthracite Woodgrain
87393 nuie Merit Wall Hung Single Door Vanity and Ceramic Basin 500mm - Hacienda Black
88178 Hudson Reed Juno 350mm Wall Hung Tall Unit Single Door - Autumn Oak
89996 nuie Mayford Floor Standing 2 Door Vanity Unit with Square Ceramic Basin 650mm - Gloss White
90809 Hudson Reed Juno Wall Hung 350mm Tall Unit - Metallic Slate