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, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (18, 16) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00045

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_descriptions",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "product_id"],
          "key": "product_id",
          "key_length": "3",
          "used_key_parts": ["product_id"],
          "rows": 2,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (18,16)",
          "attached_condition": "cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}

Result

product_id short_description full_description meta_keywords meta_description search_words promo_text unit_name
16 <p>Whether you are viewing a premium-quality 2D picture or seeing incredible 3D depth, images are breathtakingly real in Samsung Full HD. Combine with a 3D TV and 3D active shutter glasses to view the latest Hollywood 3D titles or amplify your viewing experience by upconverting 2D content to immersive 3D.</p> <p class="product-promo-text"><span class="product-promo-header">FREE US shipping over $100!</span><span class="product-promo-body">Orders within next 2 days will be shipped on Monday</span></p>
18 <p>Whether you are viewing a premium-quality 2D picture or seeing incredible 3D depth, images are breathtakingly real in Samsung Full HD. Combine with a 3D TV and 3D active shutter glasses to view the latest Hollywood 3D titles or amplify your viewing experience by upconverting 2D content to immersive 3D.</p> <p class="product-promo-text"><span class="product-promo-header">FREE US shipping over $100!</span><span class="product-promo-body">Orders within next 2 days will be shipped on Monday</span></p>