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, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (37) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00178

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_descriptions",
          "access_type": "const",
          "possible_keys": ["PRIMARY", "product_id"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["product_id", "lang_code"],
          "ref": ["const", "const"],
          "rows": 1,
          "filtered": 100
        }
      }
    ]
  }
}

Result

product_id short_description full_description unit_name
37 <p><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Технические параметры:&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Kenwood DPX308U - 2DIN CD-ресивер с USB на передней панели и AUX входы&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Управление Ipod&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Дисплей: 14 сегментный, 13 разрядный переменного цвета&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Пульт дистанционного управления&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">AM / FM тюнер&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">RBDS&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">USB вход на передней панели&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Поддержка WMA / MP3 / AAC WMA / MP3 / AAC&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">24-битный цифро-аналоговый преобразователь&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">AUX входы&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">3-полосный параметрический эквалайзер, плюс 8 предустановленных кривых эквалайзера&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">System Q&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Выход предусилителя 2Pre 2.0V @ 600&amp;#937;&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">FM Диапазон частот 87.9MHz - 107.9MHz&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">FM Полезная чувствительность 11.2dBf 11.2dBf&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Максимальная мощность 50Wx4&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Полная мощность Величина 22Wx4&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Рабочее напряжение - 14,4 (11 - 16 V допустимого)&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Максимальное потребление тока 10A&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Ширина 182 (мм)&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Высота 112 мм&nbsp;</span><br style="color: #6c6c6c; font-family: Tahoma; font-size: 13px;" /><span style="font-family: Tahoma; font-size: 13px; color: #000000;">Глубина 158 (мм)&nbsp;</span></p>