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 (
    3288, 1533, 41345, 5544, 3287, 3286, 
    65, 5543, 3289, 6181, 6093, 6180, 2183, 
    5546, 40761, 2182, 41170, 6533, 26927, 
    6550, 1786, 5973, 74, 6124, 6529, 6534, 
    26966, 6535, 26924, 26968, 6183, 26920
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00254

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 (3288,1533,41345,5544,3287,3286,65,5543,3289,6181,6093,6180,2183,5546,40761,2182,41170,6533,26927,6550,1786,5973,74,6124,6529,6534,26966,6535,26924,26968,6183,26920) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}