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.meta_keywords, 
  cscart_product_descriptions.meta_description, 
  cscart_product_descriptions.search_words, 
  cscart_product_descriptions.promo_text 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (292, 296) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00044

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "rows": 2,
      "filtered": 100,
      "index_condition": "((cscart_product_descriptions.product_id in (292,296)) and (cscart_product_descriptions.lang_code = 'en'))"
    }
  }
}

Result

product_id short_description full_description meta_keywords meta_description search_words promo_text
292 <p>2007 Nissan Navara D40 Turbo Diesel Auto 253,793kms</p> 2007, Nissan ,Navara ,D40, Turbo, Diesel ,Auto
296 <p>2010 Nissan X-Trail Turbo Diesel Auto</p><p>300,861kms</p> Nissan,X-Trail,Turbo,Diesel,Auto