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 (
    40437, 1896, 47632, 1893, 38074, 3288, 
    33310, 28159, 1894, 47631, 41345, 41341, 
    47597, 1767, 2139, 41340
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00662

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": 16,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (40437,1896,47632,1893,38074,3288,33310,28159,1894,47631,41345,41341,47597,1767,2139,41340) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}