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 (
    20669, 20670, 20671, 20672, 20673, 20674, 
    20675, 20676, 20677, 20678, 20679, 
    20680, 20681, 20682, 20683, 20684
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00034

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 (20669,20670,20671,20672,20673,20674,20675,20676,20677,20678,20679,20680,20681,20682,20683,20684) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id short_description full_description unit_name
20669 Cover assembly console top<p>Part number 84650T1100RWD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20670 Armrest Assembly-Console<p>Part number 84660T1150OWN</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20671 Lock assembly-armrest<p>Part number 84663T10004X</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20672 Cover Assembly - Console Rear<p>Part number 84640T1100NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20673 Cover assembly - console side left<p>Part number 84614T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20674 Mat-Console Storage Box<p>Part number 84616T1050</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20675 Cover assembly - console side right<p>Part number 84615T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20676 Wiring Assembly-Extension<p>Part number 91875T1030</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20677 Wiring console-extension<p>Part number 91875T1520</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20678 Switch Assy - Console Upper Cover<p>Part number 93310T1000VCS</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20679 Antenna Assembly-Smart Key<p>Part number 95460G8300</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20680 Antenna Assembly - Coil<p>Part number 93503T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20681 Unit Assembly - Wireless Charging<p>Part number 95560T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20682 Unit assembly-video recording system<p>Part number 95720T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20683 Unit assembly-video recording system<p>Part number 95720T1010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20684 Cable Assembly-USB<p>Part number 96596T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>