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 (
    27946, 3525, 3523, 2949, 3534, 1404, 
    33606, 2936, 2968, 5777, 2944, 5776, 
    32317, 2919, 3019, 2868, 37849, 1407, 
    2864, 3408, 3412, 1417, 32328, 3025, 
    1406, 32360, 3409, 19210, 27927, 35733, 
    32319, 1419
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.01269

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 (27946,3525,3523,2949,3534,1404,33606,2936,2968,5777,2944,5776,32317,2919,3019,2868,37849,1407,2864,3408,3412,1417,32328,3025,1406,32360,3409,19210,27927,35733,32319,1419) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}