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 (
    21327, 21328, 21329, 21330, 21331, 21332, 
    21333, 21334, 21335, 21336, 21337, 
    21338, 21339, 21340, 21341, 21342
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00052

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 (21327,21328,21329,21330,21331,21332,21333,21334,21335,21336,21337,21338,21339,21340,21341,21342) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
21327 Flange cover-rear combination inside, left<p>Part number 92431T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21328 Garnish-rear combination lamp, left<p>Part number 92435T6000UYH</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21329 Garnish-rear combination lamp, right<p>Part number 92436T6000UYH</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21330 Flange cover-rear combination inside, right<p>Part number 92441T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21331 BRACKET<p>Part number 92126J2000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21332 Lamp Assy-Cargo<p>Part number 92855T1100DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21333 Body assembly - room lamp<p>Part number 92813T1000VDS</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21334 Lamp assembly - rear personal, left<p>Part number 92860T1000VDS</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21335 Lamp assembly - rear personal, right<p>Part number 92870T1000VDS</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21336 Sensor Assembly - Rear Accupant Alert<p>Part number 95740T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21337 Switch assembly - multi-function<p>Part number 934D2T65804X</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21338 Switch Assembly - Side Crash Pad<p>Part number 93700T6100VCS</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21339 Cluster Assembly - Instrumentation<p>Part number 94013T6001</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21340 Nut-Flange Paint Clear<p>Part number 1336606001</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21341 Unit Assembly - Head Up Display<p>Part number 94310T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21342 Unit Assembly-L.D.C<p>Part number 95310T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>