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, 85730, 85747, 85757, 85767, 85677, 
    85737, 89455, 89468, 89476, 89484, 
    89790, 89460, 88175, 88223, 84774, 
    84787, 84796, 88172, 88220, 84778, 
    85673, 85693, 85705, 85717, 87551, 
    88404, 87460, 88500, 89453
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00110

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "13.52"
    },
    "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": 30,
      "rows_produced_per_join": 30,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "10.52",
        "eval_cost": "3.00",
        "prefix_cost": "13.52",
        "data_read_per_join": "114K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (85713,85730,85747,85757,85767,85677,85737,89455,89468,89476,89484,89790,89460,88175,88223,84774,84787,84796,88172,88220,84778,85673,85693,85705,85717,87551,88404,87460,88500,89453)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
84774 Classique Components Wall Hung 1 Drawer Unit, 800mm - Satin Anthracite
84778 Classique Components Wall Hung 1 Drawer Unit, 800mm - Satin White
84787 Classique Components Wall Hung 1 Drawer Unit, 800mm - Satin Grey
84796 Classique Components Wall Hung 1 Drawer Unit, 800mm - Satin Green
85673 nuie Deco 800mm Wall Hung Single Drawer Unit - Satin Anthracite
85677 nuie Deco 500mm Wall Hung 2-Drawer Unit - Satin White
85693 nuie Deco 800mm Wall Hung Single Drawer Unit - Satin Grey
85705 nuie Deco 800mm Wall Hung Single Drawer Unit - Satin Blue
85713 nuie Deco 500mm Wall Hung 2-Drawer Unit - Satin Green
85717 nuie Deco 800mm Wall Hung Single Drawer Unit - Satin Green
85730 Hudson Reed Fluted 800mm Wall Hung Single Drawer Unit - Satin Anthracite
85737 Hudson Reed Fluted 800mm Wall Hung Single Drawer Unit - Satin White
85747 Hudson Reed Fluted 800mm Wall Hung Single Drawer Unit - Satin Grey
85757 Hudson Reed Fluted 800mm Wall Hung Single Drawer Unit - Satin Blue
85767 Hudson Reed Fluted 800mm Wall Hung Single Drawer Unit - Satin Green
87460 nuie Athena Wall Hung 1 Drawer Vanity Unit 800mm - Gloss Grey
87551 nuie Athena Wall Hung 2 Drawer Vanity Unit 600mm - Gloss White
88172 Hudson Reed Juno 600mm Wall Hung Single Drawer Unit - Autumn Oak
88175 Hudson Reed Juno 800mm Wall Hung Single Drawer Unit - Autumn Oak
88220 Juno Components Wall Hung 1 Drawer Unit (385mm Deep), 600mm - Metallic Slate
88223 Juno Components Wall Hung 1 Drawer Unit (385mm Deep), 800mm - Metallic Slate
88404 nuie Arno 600mm Wall Hung 2-Drawer Unit - Gloss White
88500 nuie Arno 800mm Wall Hung 1-Drawer Unit - Satin Green
89453 Lunar Components Wall Hung 1 Drawer Unit, 600mm - Satin Anthracite
89455 Lunar Components Wall Hung 1 Drawer Unit, 800mm - Satin Anthracite
89460 Lunar Components Wall Hung 1 Drawer Unit, 800mm - Satin White
89468 Lunar Components Wall Hung 1 Drawer Unit, 800mm - Satin Grey
89476 Lunar Components Wall Hung 1 Drawer Unit, 800mm - Satin Blue
89484 Lunar Components Wall Hung 1 Drawer Unit, 800mm - Satin Green
89790 Hudson Reed Urban Wall Hung 2 Drawer Vanity Unit 500mm - Satin White