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 (
    21743, 21744, 21745, 21746, 21747, 21748, 
    21749, 21750, 21751, 21752, 21753, 
    21754, 21755, 21756, 21757, 21758
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00055

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 (21743,21744,21745,21746,21747,21748,21749,21750,21751,21752,21753,21754,21755,21756,21757,21758) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id short_description full_description unit_name
21743 Panel assembly - rear door trim, right<p>Part number 83306T1380NDF</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21744 Wiring Assembly - Rear Door Expansion<p>Part number 83397T1020</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21745 Wiring Assembly - Rear Door Expansion<p>Part number 83398T1020</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21746 Lamp assembly - rear door foot, right<p>Part number 93640T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21747 Label-Fuel Economy<p>Part number 324302T016</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21748 Latch assembly - rear door, left<p>Part number 81410T1200</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21749 Latch assembly - rear door, right<p>Part number 81420T1200</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21750 Glass assembly - rear door, left<p>Part number 83410T1260</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21751 Under cover assy-floor front, left<p>Part number 84213T1050</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21752 Armrest Assembly-Console<p>Part number 84660T1100OWN</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21753 Storage Box-Console<p>Part number 84680T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21754 Mat-Console Storage Box<p>Part number 84616T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21755 Wiring Assembly-Extension<p>Part number 91875T1040</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21756 Wiring assembly - loop<p>Part number 91801T1500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21757 Wiring assembly - loop<p>Part number 91831T1750</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21758 Pad-rear package tray under<p>Part number 84280T1100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>