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 (
    87244, 87245, 87246, 87249, 87250, 87251, 
    86894, 90828, 92409, 92410, 92411, 
    92412, 92413, 92414, 92415, 92232, 
    92233, 92234, 92235, 92236, 92238, 
    92468, 92472, 92473, 92474, 82338, 
    84240, 88588, 84239, 82337
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00077

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 (87244,87245,87246,87249,87250,87251,86894,90828,92409,92410,92411,92412,92413,92414,92415,92232,92233,92234,92235,92236,92238,92468,92472,92473,92474,82338,84240,88588,84239,82337)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
82337 nuie Slimline Slide Rail Kit - Chrome
82338 Hudson Reed Slide Rail Kits Linear Slide Rail Kits - Chrome
84239 nuie Athena Straight Front Panel & Plinth 1600mm - White
84240 nuie Athena Straight Front Panel & Plinth 1700mm - White
86894 Traditional Shower Tidy
87244 Old London Straight Bath End Panel 700mm - Timeless Sand
87245 Old London Straight Bath End Panel 750mm - Timeless Sand
87246 Old London Straight Bath End Panel 800mm - Timeless Sand
87249 Old London Straight Bath End Panel 700mm - Hunter Green
87250 Old London Straight Bath End Panel 750mm - Hunter Green
87251 Old London Straight Bath End Panel 800mm - Hunter Green
88588 Hudson Reed Fusion Bath Front Panel & Plinth 1700mm - Gloss White
90828 Nuie Core 600mm Thin Edge Basin 1TH
92232 BC Designs Bath Wastes Push Down Bath Waste 60mm (Unslotted) - Light Fawn
92233 BC Designs Bath Wastes Push Down Bath Waste 60mm (Unslotted) - Gunmetal
92234 BC Designs Bath Wastes Push Down Bath Waste 60mm (Unslotted) - Industrial Grey
92235 BC Designs Bath Wastes Push Down Bath Waste 60mm (Unslotted) - Khaki Green
92236 BC Designs Bath Wastes Push Down Bath Waste 60mm (Unslotted) - Mushroom
92238 BC Designs Bath Wastes Push Down Bath Waste 60mm (Unslotted) - Satin Rose
92409 BC Designs Towel Rail for Ornate Basin Stand - Brushed Chrome
92410 BC Designs Towel Rail for Ornate Basin Stand - Brushed Copper
92411 BC Designs Towel Rail for Ornate Basin Stand - Brushed Gold
92412 BC Designs Towel Rail for Ornate Basin Stand - Brushed Nickel
92413 BC Designs Towel Rail for Ornate Basin Stand - Copper
92414 BC Designs Towel Rail for Ornate Basin Stand - Gold
92415 BC Designs Towel Rail for Ornate Basin Stand - Nickel
92468 BC Designs Push Down Bath Waste 60mm (Unslotted) - Powder Blue
92472 BC Designs Push Down Bath Waste 60mm (Unslotted) - Matt White
92473 BC Designs Push Down Bath Waste 60mm (Unslotted) - Powder Grey
92474 BC Designs Push Down Bath Waste 60mm (Unslotted) - Polished White