What's the difference between a primary key and a unique key?

Both primary key and unique enforce uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the column, where unique creates a non-clustered index by default. Another major difference is that, primary key does not allow NULLs, but unique key allows one NULL only.

What is de-normalization and when would you go for it?

As the name indicates, de-normalization is the reverse process of normalization. It is the controlled introduction of redundancy in to the database design. It helps improve the query performance as the number of joins could be reduced.

What are clustered index and non clustered index

With a clustered index the rows are stored physically on the disk in the same order as the index. There can therefore be only one clustered index.

With a non clustered index there is a second list that has pointers to the physical rows. You can have many non clustered indexes, although each new index will increase the time it takes to write new records.

It is generally faster to read from a clustered index if you want to get back all the columns. You do not have to go first to the index and then to the table.

Writing to a table with a clustered index can be slower, if there is a need to rearrange the data.

In other words,
A clustered index means you are telling the database to store close values actually close to one another on the disk. This has the benefit of rapid scan / retrieval of records falling into some range of clustered index values.


From Wikipedia :
A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of slower writes and increased storage space

Silence Removal and End Point Detection MATLAB Code

Visit http://ganeshtiwaridotcomdotnp.blogspot.com/2011/06/final-report-text-prompted-remote.html for more detail about our project.
For the purpose of silence removal of captured sound, we used the algorithm specified in
"A New Silence Removal and Endpoint Detection Algorithm for Speech and Speaker Recognition Applications"
Our actual system was in JAVA but we verified the performance of this algorithm in MATLAB.

Inputs and Output

Before silence removal

After automatic silence removal

Here is the Matlab code : 
It first records sound for 5 seconds and removes the silence and then plays back.

Logic Design of Digital Clock, assignment on logic circuits

Logic Design of Digital Clock, assignment on logic circuits

Logic Design of Exhibition hall visitor density counter

Logic Design of Exhibition hall visitor density counter

History of UNIX like OS : Assignment Article

History of UNIX Like OS Assignment

Logic Design of 8-bit arithmetic microprocessor : an assignment on CAD

Logic Design of 8-Bit Arithmetic Microprocessor

BlueChess : Two Player Chess Game in J2ME, My minor project @ IOE

Here is the download link for BlueChess : Two Player Chess Game

http://www.4shared.com/file/JWiI8Cce/BlueChess_Bluetooth_two_player.html

XML parsing using SaxParser with complete code

SAX parser use callback function (org.xml.sax.helpers.DefaultHandler) to informs clients of the XML document structure. You should extend DefaultHandler and override few methods to achieve xml parsing.
The methods to override are

• startDocument() and endDocument() – Method called at the start and end of an XML document. 
• startElement() and endElement() – Method called at the start and end of a document element.  
• characters() – Method called with the text contents in between the start and end tags of an XML document element.

The following example demonstrates the uses of DefaultHandler to parse and XML document. It performs mapping of xml to model class and generate list of objects.