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 (
    100466, 100467, 100468, 100469, 100470, 
    100471, 100472, 100473, 100474, 100475, 
    100476, 100923, 100924, 100925, 100926, 
    100927, 100928, 100929, 100930, 100931, 
    100932, 100933, 100934, 100935
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00085

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "10.82"
    },
    "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": 24,
      "rows_produced_per_join": 24,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "8.42",
        "eval_cost": "2.40",
        "prefix_cost": "10.82",
        "data_read_per_join": "91K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (100466,100467,100468,100469,100470,100471,100472,100473,100474,100475,100476,100923,100924,100925,100926,100927,100928,100929,100930,100931,100932,100933,100934,100935)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}