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 (
    20861, 20862, 20863, 20864, 20865, 20866, 
    20867, 20868, 20869, 20870, 20871, 
    20872, 20873, 20874, 20875, 20876
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00047

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 (20861,20862,20863,20864,20865,20866,20867,20868,20869,20870,20871,20872,20873,20874,20875,20876) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id short_description full_description unit_name
20861 Bolt-seatbelt anchor mounting<p>Part number 89811D2100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20862 Seat belt assembly - rear, center<p>Part number 89850T1300NWA</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20863 Seat Belt Assembly - Rear Right<p>Part number 89820T1000NWA</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20864 Seat Belt Assembly - Rear Left<p>Part number 89810T1000NWA</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20865 Buckle assembly-rear seat belt, left<p>Part number 89830T1000OWN</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20866 Buckle assembly - rear seat belt, right<p>Part number 89840T1000OWN</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20867 Buckle Assembly - Center Seat Belt<p>Part number 89860T1000OWN</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20868 Wiring Assembly-Main<p>Part number 91101T1442</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20869 Junction box assembly - instrument panel<p>Part number 91951T1250</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20870 Low profile 40A fuse<p>Part number 1879001124</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20871 Fuse - Slow Blow Micro 30A<p>Part number 1879004933</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20872 Upper Cover - Engine Room Junction Box<p>Part number 919B5T1200</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20873 Wiring Assembly-Front<p>Part number 91201T1092</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20874 Bracket-wiring mounting<p>Part number 91931T1320</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20875 Upper Cover - Fuse & Relay Engine<p>Part number 91956T1200</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20876 Upper Cover - Engine Room Box<p>Part number 91956T1101</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>