Java - Sorting Algorithms

The animations on this URL illustrate a number of different sequential and parallel sorting algorithms. The relative execution times of the animations give a very rough idea of the relative speeds of the algorithms. Each algorithm is finished when its colored lines disappear.

To see animation, you need Java Runtime Enviroment.

How Oracle Hash Join works?

Hash Join is one of join used by Oracle server when we joine multiple table. Following link will give you a demo on Flash. This demo explains how Hash Join works in Oracle.
This demo was created by TomKyte from Oracle. I got this link from AskTom.

http://tinyurl.com/l2qsh

Alternatively, if you want "offline viewing" of this, you can download a .exe
file (about 1.8mb) that lets you play this whenever you want:

http://tinyurl.com/nyjro

Nagios

Nagios is a host and service monitor designed to inform you of network problems before your clients, end-users or managers do. It has been designed to run under the Linux operating system, but works fine under most *NIX variants as well. The monitoring daemon runs intermittent checks on hosts and services you specify using external "plugins" which return status information to Nagios. When problems are encountered, the daemon can send notifications out to administrative contacts in a variety of different ways (email, instant message, SMS, etc.). Current status information, historical logs, and reports can all be accessed via a web browser.

Nagios is licensed under the terms of the GNU General Public License Version 2 as published by the Free Software Foundation. This gives you legal permission to copy, distribute and/or modify Nagios under certain conditions. Read the 'LICENSE' file in the Nagios distribution or read the online version of the license for more details. Nagios is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE WARRANTY OF DESIGN, MERCHANTABILITY, AND FITNESS FOR A PARTICULAR PURPOSE.

VPN Solution - Hamachi , OpenVPN

Hamachi is a great program that enables you to easily set up an encrypted private network between remote computers over the open internet. It's a simple elegant solution without much fuss. It does have some limitations, but it's definitely an easy and secure way to access your shared folders, enable remote network gaming, and control your machines via Remote Desktop or VNC type programs.

Nice tutorial, how to setup Hamachi is available here.

OpenVPN is a full-featured SSL VPN which implements OSI layer 2 or 3 secure network extension using the industry standard SSL/TLS protocol, supports flexible client authentication methods based on certificates, smart cards, and/or username/password credentials, and allows user or group-specific access control policies using firewall rules applied to the VPN virtual interface. OpenVPN is not a web application proxy and does not operate through a web browser.

Oracle Tip - SQL Order by clause with CASE

How to use CASE in ORDER BY clause of SELECT statement in Oracle SQL.
Order By clause allow you display data in ASCENDING or DESCENDING.

Using Order By clause we can able to arrange data in ASCENDING or DESCENDING based on columns. If it is VARCHAR2 column for ASCENDIGN and DESCENDING data will be sorted by Alphabetical. What if we want to sort CUSTOM Sort, not Alphabetically ascending or descending.

For example, take the following SQL. We can display CITY column either in Alphabetically ASC or DESC.

SQL with ORDER BY CITY ASC:
===========================

select city from (
select
'San Francisco' a from dual
union all
Select 'Boston' a from dual
union all
Select 'Charlotte' a from dual
union all
Select 'Phoenix' a from dual
union all
Select 'Houston' a from dual
union all
Select 'Washington DC' a from dual)
order by city ASC

Now let us see how we can do Custom Sorting using CASE clause in ORDER BY Clause.
We want to get list of city in the follwoing order, then we will use the following SQL.

CITY
=====
Charlotte
Boston
Phoenix
Washington DC
Houston
San Francisco


SQL with CUSTOM Sorting.
========================

select city from (
select
'San Francisco' a from dual
union all
Select 'Boston' a from dual
union all
Select 'Charlotte' a from dual
union all
Select 'Phoenix' a from dual
union all
Select 'Houston' a from dual
union all
Select 'Washington DC' a from dual)
order by CASE a when 'Charlotte' then 1
when 'Boston' then 2
when 'Phoenix' then 3
when 'Washington DC' then 4
when 'Houston' then 5
end;


Please note that in CASE clause, I never mentioned about 'San Francisco' city. But the SQL will bring 'San Francisco' as last city in the record set.

This may be required sometimes, we want to display in DropDown List box in frontend applications.

Oracle - Jonathan Lewis blog

Jonathan Lewis started blogging since last week. I need to track his blog every day.

Nice blog for Oracle tips