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 (
    21727, 21728, 21729, 21730, 21731, 21732, 
    21733, 21734, 21735, 21736, 21737, 
    21738, 21739, 21740, 21741, 21742
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00042

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 (21727,21728,21729,21730,21731,21732,21733,21734,21735,21736,21737,21738,21739,21740,21741,21742) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id short_description full_description unit_name
21727 Pad-antinoise<p>Part number 81684T1500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21728 Harness-Panorama Roof<p>Part number 81685T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21729 Bracket-panoramic roof side, right<p>Part number 81696T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21730 Bracket-panoramic roof side, left<p>Part number 81695T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21731 SCREW-SUNROOF<p>Part number 81682T1400</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21732 Tapping screw-washer assembly<p>Part number 8229026000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21733 Panel assembly - front door trim, right<p>Part number 82306T1540NDF</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21734 Panel assembly - front door trim, left<p>Part number 82305T1540NDF</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21735 Wiring Assembly - Front Door Expansion<p>Part number 82397T1020</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21736 Wiring Assembly - Front Door Expansion<p>Part number 82398T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21737 Speaker assembly - tweeter, left<p>Part number 96310T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21738 Speaker assembly - tweeter, right<p>Part number 96311T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21739 Latch assembly - front door, left<p>Part number 81310T1010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21740 Latch assembly - front door, right<p>Part number 81320T1020</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21741 Weather strip assembly-rear door side, right<p>Part number 83140T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21742 Panel assembly - rear door trim, left<p>Part number 83305T1380NDF</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>