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 (
    88418, 89787, 89791, 88754, 88942, 85664, 
    85684, 85696, 85708, 85669, 85689, 
    85701
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00050

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "5.41"
    },
    "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": 12,
      "rows_produced_per_join": 12,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "4.21",
        "eval_cost": "1.20",
        "prefix_cost": "5.41",
        "data_read_per_join": "45K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (88418,89787,89791,88754,88942,85664,85684,85696,85708,85669,85689,85701)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
85664 nuie Deco 600mm Floor Standing 2-Door Unit - Satin Anthracite
85669 nuie Deco 500mm Wall Hung 2-Drawer Unit - Satin Anthracite
85684 nuie Deco 600mm Floor Standing 2-Door Unit - Satin Grey
85689 nuie Deco 500mm Wall Hung 2-Drawer Unit - Satin Grey
85696 nuie Deco 600mm Floor Standing 2-Door Unit - Satin Blue
85701 nuie Deco 500mm Wall Hung 2-Drawer Unit - Satin Blue
85708 nuie Deco 600mm Floor Standing 2-Door Unit - Satin Green
88418 nuie Arno 600mm Floor Standing 2-Drawer Unit - Gloss White
88754 Hudson Reed Fusion Fitted Floor Standing 2 Door Vanity Unit Compact 500mm - Gloss Grey
88942 Hudson Reed Quartet 2 Tap Hole Polymarble Double Basin 1400mm
89787 Hudson Reed Urban Floor Standing 2 Door 1 Drawer Vanity Unit 600mm - Satin White
89791 Hudson Reed Urban 600mm Wall Hung 2-Drawer Unit - Satin White