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 (
    20717, 20718, 20719, 20720, 20721, 20722, 
    20723, 20724, 20725, 20726, 20727, 
    20728, 20729, 20730, 20731, 20732
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00035

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 (20717,20718,20719,20720,20721,20722,20723,20724,20725,20726,20727,20728,20729,20730,20731,20732) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id short_description full_description unit_name
20717 Sun visor assembly, right<p>Part number 85220T1BH0NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20718 Plug-trim mounting<p>Part number 857463L000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20719 Feeder Cable-Antenna Floor NO.1<p>Part number 96230T1220</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20720 Pad-rear package tray under<p>Part number 84280T1300</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20721 Trim Assembly - Package Tray<p>Part number 85610T1DK0NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20722 Trim Assembly - Package Tray<p>Part number 85625T1400NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20723 Sunshade assembly-rear<p>Part number 85690T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20724 Bezel Assembly - Child Anchor<p>Part number 89897G8100NNB</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20725 Mobility Kit - Tires<p>Part number 52933D4000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20726 Tire Mobility Kit Hose Assembly<p>Part number 52935D4000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20727 Partition Assembly - Panel & Trim<p>Part number 84297T1010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20728 Mat assembly-luggage covering<p>Part number 85710T1000NNB</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20729 Board assembly - luggage covering<p>Part number 85715T1000NNB</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20730 Trim-luggage partition<p>Part number 85720T1000NNB</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20731 Trim assembly - luggage side, left<p>Part number 85730T1000NNB</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20732 Cover-luggage side right<p>Part number 85748T1000NNB</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>