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 (
    846, 817, 816, 787, 819, 781, 760, 758, 
    752, 751, 750, 749, 747, 732, 731, 723, 
    717, 707, 673, 650, 647, 644, 641, 639, 
    636, 624, 616, 210, 197, 155, 51
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00061

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "21.71"
    },
    "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",
      "index_condition": "((`betaatif_store`.`cscart_product_descriptions`.`product_id` in (846,817,816,787,819,781,760,758,752,751,750,749,747,732,731,723,717,707,673,650,647,644,641,639,636,624,616,210,197,155,51)) and (`betaatif_store`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "18.61",
        "eval_cost": "3.10",
        "prefix_cost": "21.71",
        "data_read_per_join": "118K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ]
    }
  }
}