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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 (54) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_descriptions",
          "access_type": "const",
          "possible_keys": ["PRIMARY", "product_id"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["product_id", "lang_code"],
          "ref": ["const", "const"],
          "rows": 1,
          "filtered": 100
        }
      }
    ]
  }
}

Result

product_id	short_description	full_description	meta_keywords	meta_description	search_words	promo_text	unit_name
54		<p>The TS-W3002D2/4 subwoofers are designed to produce enormously powerful music. Just take a look at its super-heavy-duty construction, all designed to handle up to 3,500 watts max. Double-stacked magnets for higher power, and a step-up radial surround for superior control and long excursions. We used a constructed cast-aluminum basket for this sub. Add in our patented IMPP cone and you've got a monster sub that can handle whatever you want to throw at it.</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>