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 (
    5626, 31954, 35654, 31955, 45259, 33070, 
    31956, 48828, 48565, 48954, 47271, 
    48956, 48955, 48829, 48959, 48958, 
    48661, 48660, 48663, 48659, 48662, 
    49483
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00166

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_descriptions",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "product_id"],
          "key": "PRIMARY",
          "key_length": "11",
          "used_key_parts": ["product_id", "lang_code"],
          "rows": 22,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (5626,31954,35654,31955,45259,33070,31956,48828,48565,48954,47271,48956,48955,48829,48959,48958,48661,48660,48663,48659,48662,49483) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}