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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.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (184, 183, 164) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "7.21"
    },
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "9",
      "rows_examined_per_scan": 3,
      "rows_produced_per_join": 3,
      "filtered": "100.00",
      "index_condition": "((`rajansecarter_15_june_mve`.`cscart_product_descriptions`.`product_id` in (184,183,164)) and (`rajansecarter_15_june_mve`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "6.61",
        "eval_cost": "0.60",
        "prefix_cost": "7.21",
        "data_read_per_join": "13K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description",
        "unit_name"
      ]
    }
  }
}

Result

product_id	short_description	full_description	unit_name
164		<p>When shooting in low light, zooming in on a shot, or when your camera is unsteady, Optical Image Stabilization helps eliminate blurry results. This feature stabilizes your photos by changing their path to the image sensor before they are recorded digitally. Your photos come out sharp and ideally focused.</p>
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>
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>