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 (
    88054, 87990, 87961, 87875, 87937, 87950, 
    87959, 88798, 90826, 87952, 88004, 
    87998
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00050

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "6.72"
    },
    "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": "5.52",
        "eval_cost": "1.20",
        "prefix_cost": "6.72",
        "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 (88054,87990,87961,87875,87937,87950,87959,88798,90826,87952,88004,87998)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
87875 nuie Mayford Round Ceramic 1 Tap Hole Basin 650mm
87937 Hudson Reed Chancery Cistern
87950 nuie Lawton Curved Cistern
87952 nuie Lawton New Cistern
87959 nuie Ambrose 450mm Basin 1 Tap Hole
87961 nuie Ambrose 500mm Basin 1 Tap Hole
87990 nuie Bliss Square 520mm Basin 1 Tap Hole
87998 nuie Provost 420mm Small Basin 1 Tap Hole
88004 nuie Harmony Cistern & Fittings
88054 Hudson Reed Richmond Wall Hung 3 Tap Hole Basin 595mm
88798 Hudson Reed Fusion Fitted Decorative End Panel - Gloss Grey
90826 Nuie Core 400mm Thin Edge Basin 1TH