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 (
    20925, 20926, 20927, 20928, 20929, 20930, 
    20931, 20932, 20933, 20934, 20935, 
    20936, 20937, 20938, 20939, 20940
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00068

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 (20925,20926,20927,20928,20929,20930,20931,20932,20933,20934,20935,20936,20937,20938,20939,20940) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
20925 Lamp-rear combination outside, right<p>Part number 92420T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20926 Cover-rear combination lamp, left<p>Part number 92411T1001</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20927 Cover-rear combination lamp, left<p>Part number 92431T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20928 Cover-rear combination lamp, right<p>Part number 92421T1001</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20929 Cover-rear combination lamp, right<p>Part number 92441T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20930 Garnish-rear combination lamp, left<p>Part number 92435T1000MDY</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20931 Garnish-rear combination lamp, right<p>Part number 92436T1000MDY</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20932 Lamp Assembly - High Mounted Stop<p>Part number 92700T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20933 Body assembly - room lamp<p>Part number 92813T1030VDS</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20934 Bracket-mounting support, left<p>Part number 92846T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20935 Bracket-mounting support, right<p>Part number 92847T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20936 Bracket-unit support<p>Part number 92849T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20937 Lamp assembly - rear personal, left<p>Part number 92860T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20938 Lamp assembly - rear personal, right<p>Part number 92870T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20939 Lamp Assembly-Vanity<p>Part number 92890D2500NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20940 Sensor Assembly - Rear Accupant Alert<p>Part number 95740JI000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>