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 (
    21133, 21134, 21135, 21136, 21137, 21138, 
    21139, 21140, 21141, 21142, 21143, 
    21144, 21145, 21146, 21147, 21148
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00924

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 (21133,21134,21135,21136,21137,21138,21139,21140,21141,21142,21143,21144,21145,21146,21147,21148) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id short_description full_description unit_name
21133 Rack assembly-loop, left<p>Part number 87270T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21134 Rack assembly-loop, right<p>Part number 87280T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21135 Lamp Assembly - High Mounted Stop<p>Part number 92700T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21136 Nozzle Assembly-Rear Washer<p>Part number 98930T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21137 Tapping screw - flange head<p>Part number 1249204147B</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21138 Pad-Antinoise N0.3<p>Part number 87323T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21139 Pad-antinoise<p>Part number 86618B1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21140 Emblem-GV80<p>Part number 86310T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21141 Emblem-AWD<p>Part number 86316T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21142 Emblem-GENESIS<p>Part number 86311T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21143 Strip-tailgate side, left<p>Part number 87313T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21144 Strip - tailgate side, right<p>Part number 87314T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21145 Pad-Tail Gate Garnish<p>Part number 87318T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21146 Pad-sealing<p>Part number 87319T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21147 Pad-Trunk Lid Garnish<p>Part number 87369T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21148 Strip-Tailgate Garnish<p>Part number 87315T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>