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 (
    20605, 20606, 20607, 20608, 20609, 20610, 
    20611, 20612, 20613, 20614, 20615, 
    20616, 20617, 20618, 20619, 20620
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00036

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id", "idx_product_lang"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "rows": 16,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (20605,20606,20607,20608,20609,20610,20611,20612,20613,20614,20615,20616,20617,20618,20619,20620) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
20605 Weather strip - rear door lower, right<p>Part number 83180T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20606 Weather strip - lower rear door, left<p>Part number 83170T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20607 Panel assembly - rear door trim, left<p>Part number 83305T1390NDF</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20608 Panel assembly - rear door trim, right<p>Part number 83306T1390NDF</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20609 Curtain-rear door, left<p>Part number 83915T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20610 Curtain-rear door, right<p>Part number 83916T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20611 Cab-rear door pull handle, left<p>Part number 83714T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20612 Cab-rear door pull handle, right<p>Part number 83724T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20613 Cover assembly - rear door frame, left<p>Part number 83910T10104X</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20614 Cover assembly - rear door frame, right<p>Part number 83920T10104X</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20615 Wiring Assembly - Rear Door Expansion<p>Part number 83397T1030</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20616 Wiring Assembly - Rear Door Expansion<p>Part number 83398T1030</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20617 Lamp assembly - rear door foot, left<p>Part number 93630T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20618 Unit assembly - power window sub, left<p>Part number 93581T1500VCS</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20619 Speaker assembly - rear tweeter, left<p>Part number 96315T1500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20620 Speaker assembly - rear tweeter, right<p>Part number 96316T1500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>