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 (
    951, 41016, 16528, 41384, 4294, 987, 
    3722, 42180, 41409, 4290, 42161, 35691, 
    4284, 41414, 41413, 42184, 4296, 956, 
    988, 41408, 32683, 793, 4293, 4291, 
    41015, 5595, 42188, 41020, 41415, 4281, 
    41412, 41401
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.01810

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": 32,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (951,41016,16528,41384,4294,987,3722,42180,41409,4290,42161,35691,4284,41414,41413,42184,4296,956,988,41408,32683,793,4293,4291,41015,5595,42188,41020,41415,4281,41412,41401) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}