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 (
    21951, 21952, 21953, 21954, 21955, 21956, 
    21957, 21958, 21959, 21960, 21961, 
    21962, 21963, 21964, 21965, 21966
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00036

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 (21951,21952,21953,21954,21955,21956,21957,21958,21959,21960,21961,21962,21963,21964,21965,21966) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id short_description full_description unit_name
21951 Hose Assembly - Degassing<p>Part number 254W0T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21952 Thermal Management Module<p>Part number 256003N150</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21953 screw-tapping<p>Part number 28189T6350</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21954 Clamp-Hose<p>Part number 1471606500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21955 Cleaner assembly-air, left<p>Part number 28110T6320</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21956 Cleaner assembly-air, right<p>Part number 28120T6320</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21957 Filter - Air Cleaner<p>Part number 28113T6310</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21958 Hose assembly - air intake, left<p>Part number 28130T6310</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21959 Hose assembly - air intake, right<p>Part number 28140T6310</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21960 insulator<p>Part number 28160T6310</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21961 Duct assembly-air, left<p>Part number 28210T6310</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21962 Duct Assembly-Air, Right<p>Part number 28220T6310</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21963 pad<p>Part number 282PDT6210</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21964 pad<p>Part number 282PDT6220</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21965 reservoir tank bracket<p>Part number 282583N101</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21966 Hose & Pipe Assembly-Intercooler Inlet<p>Part number 282723N201</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>