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 (
    100035, 100036, 100037, 100038, 100039, 
    100040, 100041, 100042, 100043, 100044, 
    100045, 100046, 100047, 100048, 100049, 
    100050, 100051, 100052, 100053, 100054, 
    100055, 100056, 100057, 100058, 100059, 
    100060, 100061, 100062, 100063, 100064, 
    100065, 100066, 100073, 100074, 100075, 
    100076, 100077, 100078, 100079, 100080, 
    100081, 100082, 100083, 100084, 100085, 
    100086, 100087, 100088
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00128

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "21.63"
    },
    "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": 48,
      "rows_produced_per_join": 48,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "16.83",
        "eval_cost": "4.80",
        "prefix_cost": "21.63",
        "data_read_per_join": "183K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (100035,100036,100037,100038,100039,100040,100041,100042,100043,100044,100045,100046,100047,100048,100049,100050,100051,100052,100053,100054,100055,100056,100057,100058,100059,100060,100061,100062,100063,100064,100065,100066,100073,100074,100075,100076,100077,100078,100079,100080,100081,100082,100083,100084,100085,100086,100087,100088)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
100035
100036
100037
100038
100039
100040
100041
100042
100043
100044
100045
100046
100047
100048
100049
100050
100051
100052
100053
100054
100055
100056
100057
100058
100059
100060
100061
100062
100063
100064
100065
100066
100073
100074
100075
100076
100077
100078
100079
100080
100081
100082
100083
100084
100085
100086
100087
100088