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 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    100615, 100617, 100620, 100623, 100625, 
    100628, 100630, 100632, 100634, 100636, 
    100638, 100640, 100643, 100647, 100879, 
    100882, 100888, 100889, 100892, 100896, 
    100898, 100905, 100911, 101110, 101111, 
    101119, 101120, 101128, 101129, 101512, 
    101513, 101521, 101522, 101530, 101531, 
    101550, 101551, 101559, 101560, 101568, 
    101569, 101794, 101795, 101796, 101797, 
    101798, 101799, 101800, 101801, 101802, 
    101803
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00102

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "22.98"
    },
    "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": 51,
      "rows_produced_per_join": 51,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "17.88",
        "eval_cost": "5.10",
        "prefix_cost": "22.98",
        "data_read_per_join": "194K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (100615,100617,100620,100623,100625,100628,100630,100632,100634,100636,100638,100640,100643,100647,100879,100882,100888,100889,100892,100896,100898,100905,100911,101110,101111,101119,101120,101128,101129,101512,101513,101521,101522,101530,101531,101550,101551,101559,101560,101568,101569,101794,101795,101796,101797,101798,101799,101800,101801,101802,101803)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}