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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 (
    403, 404, 405, 406, 407, 408, 409, 410, 
    411, 412, 413, 414, 415, 416, 417, 418, 
    419, 420, 421, 422, 423, 424, 425, 426, 
    68
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00064

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "60.01"
    },
    "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": 25,
      "rows_produced_per_join": 25,
      "filtered": "100.00",
      "index_condition": "((`pankajecarter_systemfour`.`cscart_product_descriptions`.`product_id` in (403,404,405,406,407,408,409,410,411,412,413,414,415,416,417,418,419,420,421,422,423,424,425,426,68)) and (`pankajecarter_systemfour`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "55.01",
        "eval_cost": "5.00",
        "prefix_cost": "60.01",
        "data_read_per_join": "114K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description",
        "unit_name"
      ]
    }
  }
}

Result

product_id	short_description	full_description	unit_name
68		<p>In the right hands, amazing things happen.<br /><br />Put emails in their place<br /> Combine your personal inboxes while keeping your work account separate.<br /><br />Plenty of room in the office<br /> Microsoft® Office Mobile and multitasking on a huge <br /> 4.7" screen makes plenty of room for work, wherever you go.<br /><br />Focus on thoughts, not thumbs<br /> With such a spacious keypad, you can stop focusing on your fingers and start focusing on ideas.<br /><br />Expansive display, infinite possibility<br /> Whether you’re taking care of business or taking a break from it all, you can see the big picture on the 4.7" LCD screen.<br /><br />Pocket-sized profile<br /> At 9.9mm, it’s slim enough to fit comfortably in your pocket. But considering everything the HTC TITAN with Windows Phone is capable of, it won’t be spending much time there.</p>
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426