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 (
    19997, 19998, 19999, 20000, 20001, 20002, 
    20003, 20004, 20005, 20006, 20007, 
    20008, 20009, 20010, 20011, 20012
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00033

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 (19997,19998,19999,20000,20001,20002,20003,20004,20005,20006,20007,20008,20009,20010,20011,20012) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id short_description full_description unit_name
19997 horn plate assembly<p>Part number 56140T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
19998 Bezel Assembly - Steering Wheel<p>Part number 56171T6000DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
19999 Motor Assembly - Steering Wheel Haptics<p>Part number 56184T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20000 Extension wire (left)<p>Part number 56190T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20001 Steering Wheel Remote Control Bezel Assembly<p>Part number 96700T6850VCS</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20002 Switch assembly - paddle shifters, left<p>Part number 96770T6000VCS</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20003 Switch assembly - paddle shifters, right<p>Part number 96780T6000VCS</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20004 Column assembly-steering<p>Part number 56310T1700</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20005 Joint assembly - steering<p>Part number 56400T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20006 Joint Assembly - Universal<p>Part number 56400T6500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20007 Unit Assembly - TILT & TELE<p>Part number 95490T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20008 Module assembly - steering wheel airbag<p>Part number 80100T6100DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20009 Airbag Assembly - Passenger Seat<p>Part number 80310T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20010 Curtain airbag module, left<p>Part number 80410T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20011 Curtain airbag module, right<p>Part number 80420T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20012 End Assemblies - Tie Rods<p>Part number 56820T1100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>