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 (
    101517, 101523, 101526, 101532, 101535, 
    101552, 101555, 101561, 101564, 101570, 
    101573, 101824, 101825, 101826, 101827, 
    101828, 101829, 101830, 101831, 101832, 
    101833, 101844, 101845, 101846, 101847, 
    101848, 101849, 101850, 101851, 101852, 
    101853
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00075

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "13.97"
    },
    "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": 31,
      "rows_produced_per_join": 31,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "10.87",
        "eval_cost": "3.10",
        "prefix_cost": "13.97",
        "data_read_per_join": "118K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (101517,101523,101526,101532,101535,101552,101555,101561,101564,101570,101573,101824,101825,101826,101827,101828,101829,101830,101831,101832,101833,101844,101845,101846,101847,101848,101849,101850,101851,101852,101853)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}