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 (
    85713, 88969, 88970, 88973, 88974, 85730, 
    85747, 85757, 85767, 84765, 85660, 
    85677, 88554, 88660, 88661, 88707, 
    88708, 85721, 85738, 85748, 85758, 
    85737, 89455, 89468
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00057

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 (85713,88969,88970,88973,88974,85730,85747,85757,85767,84765,85660,85677,88554,88660,88661,88707,88708,85721,85738,85748,85758,85737,89455,89468)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
84765 Classique Components Floor Standing 2 Door Unit, 800mm - Satin White
85660 nuie Deco 600mm Floor Standing 2-Door Unit - Satin White
85677 nuie Deco 500mm Wall Hung 2-Drawer Unit - Satin White
85713 nuie Deco 500mm Wall Hung 2-Drawer Unit - Satin Green
85721 Hudson Reed Fluted 500mm Floor Standing 2-Door Unit - Satin Anthracite
85730 Hudson Reed Fluted 800mm Wall Hung Single Drawer Unit - Satin Anthracite
85737 Hudson Reed Fluted 800mm Wall Hung Single Drawer Unit - Satin White
85738 Hudson Reed Fluted 500mm Floor Standing 2-Door Unit - Satin Grey
85747 Hudson Reed Fluted 800mm Wall Hung Single Drawer Unit - Satin Grey
85748 Hudson Reed Fluted 500mm Floor Standing 2-Door Unit - Satin Blue
85757 Hudson Reed Fluted 800mm Wall Hung Single Drawer Unit - Satin Blue
85758 Hudson Reed Fluted 500mm Floor Standing 2-Door Unit - Satin Green
85767 Hudson Reed Fluted 800mm Wall Hung Single Drawer Unit - Satin Green
88554 Hudson Reed Fusion Fitted Floor Standing 2 Door Vanity Unit 800mm - Gloss White
88660 Hudson Reed Fusion Fitted Floor Standing 2 Door Vanity Unit 500mm - Anthracite Woodgrain
88661 Hudson Reed Fusion Fitted Floor Standing 2 Door Vanity Unit Compact 600mm - Anthracite Woodgrain
88707 Hudson Reed Fusion Fitted Floor Standing 2 Door Vanity Unit 500mm - Hacienda Black
88708 Hudson Reed Fusion Fitted Floor Standing 2 Door Vanity Unit Compact 600mm - Hacienda Black
88969 Hudson Reed Fusion Left Hand Round Semi-Recessed 1 Tap Hole Polymarble Basin 1100mm
88970 Hudson Reed Fusion Right Hand Round Semi-Recessed 1 Tap Hole Polymarble Basin 1100mm
88973 Hudson Reed Fusion Left Hand Square Semi-Recessed 1 Tap Hole Polymarble Basin 1100mm
88974 Hudson Reed Fusion Right Hand Square Semi-Recessed 1 Tap Hole Polymarble Basin 1100mm
89455 Lunar Components Wall Hung 1 Drawer Unit, 800mm - Satin Anthracite
89468 Lunar Components Wall Hung 1 Drawer Unit, 800mm - Satin Grey