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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 (190, 189, 184, 183) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00041

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": 4,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (190,189,184,183)",
          "attached_condition": "cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}

Result

product_id	full_description	promo_text
183	<p>The Samsung T50200SB 50-200mm Telephoto OIS Lens is a long telephoto zoom lens compatible with our NX Series of digital cameras.</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>
184	<p>Samsung’s compact 30mm pancake lens is the brightest in its class. With its 30mm fixed focal length and maximum aperture of F/2, you can capture exceptionally bright images — even in low-light situations such as shady forest paths and indoor weddings. You can also create striking, images with shallow depth of field in a variety of settings. And since it’s incredibly slim and lightweight, you can take it with you everywhere.</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>
189	<p>Fast aperture, high-performance, ultra-wide-angle zoom optimized for FX- and DX-format sensors featuring Nikon’s exclusive ED Glass and Nano Crystal Coat.</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>
190	<p>This ultra wide-angle lens, designed exclusively for use with Nikon’s DX-format, provides a versatile wide-angle zoom perspective.</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>