如何设置一个字段的值等于其他两个字段值的拼接

 conn = mysql.connector.connect(host='localhost', user='username', password='password', database='database_name')

 cursor = conn.cursor()

 update_query = "UPDATE table_name SET field_name = CONCAT(column1, column2)"

 cursor.execute(update_query)

 conn.commit()

 cursor.close()

 conn.close()

 ```

 public class UpdateField {

     public static void main(String[] args) {

         String url = "jdbc:mysql://localhost:3306/database_name";

         String username = "username";

         String password = "password";

         try {

             Connection conn = DriverManager.getConnection(url, username, password);

             Statement stmt = conn.createStatement();

             String updateQuery = "UPDATE table_name SET field_name = CONCAT(column1, column2)";

             stmt.executeUpdate(updateQuery);

             stmt.close();

             conn.close();

         } catch (SQLException e) {

             e.printStackTrace();

         }

     }

 }

 ```