SELECT 
  product_descriptions.product_id, 
  product_descriptions.short_description, 
  IF(
    product_descriptions.short_description = '' 
    OR product_descriptions.short_description IS NULL, 
    product_descriptions.full_description, 
    ''
  ) AS full_description 
FROM 
  product_descriptions 
WHERE 
  product_descriptions.product_id IN (226228, 258228, 234207) 
  AND product_descriptions.lang_code = 'en'

Query time 0.00064

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "2.51"
    },
    "table": {
      "table_name": "product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "11",
      "rows_examined_per_scan": 3,
      "rows_produced_per_join": 3,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "2.21",
        "eval_cost": "0.30",
        "prefix_cost": "2.51",
        "data_read_per_join": "15K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`goimagine`.`product_descriptions`.`product_id` in (226228,258228,234207)) and (`goimagine`.`product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
226228 <p>This blue beauty is an acrylic painting on a 12x12 inch canvas&nbsp;. Bold shades of blues with surprising pops of silver sparkle, make this a decor piece that will surely draw attention.&nbsp;</p> <p>The painting is varnished, fully cured and ready to be shipped to you!</p>
234207 <p>This monochrome beauty is an acrylic painting on a 12x12 inch canvas. Several different techniques brought together make this a decor piece that will surely draw attention.&nbsp;</p> <p>The painting is varnished, fully cured and ready to be shipped to you!</p> <p></p>
258228 <p>Black, white and neon pink - an incredible combo that makes this flower pop!</p> <p>This painting was created using the Bottle Bottom technique on a&nbsp;12x12in canvas. The acrylic paints I used are super-glossy! Because of the mega-shininess, the pictures do not do this painting justice.</p> <p>The painting is varnished, fully cured and ready to be shipped to you!</p>