What is Referential Integrity?

Referential integrity is a database concept that ensures that relationships between tables remain consistent. When one table has a foreign key to another table, the concept of referential integrity states that you may not add a record to the table that contains the foreign key unless there is a corresponding record in the linked table. It also includes the techniques known as cascading update and cascading delete, which ensure that changes made to the linked table are reflected in the primary table.

Reference: http://databases.about.com/cs/administration/g/refintegrity.htm

Stop Youtube from displaying related videos once playback of the initial video starts

To stop displaying related videos we can add a parameter (rel=0 for stop displaying) to the url of the embedded code provided by you tube. See example below

http://www.youtube.com/v/u1zgFlCw8Aw&fs=1&rel=0

For complete list of parameters check the following Google API site:

http://code.google.com/apis/youtube/player_parameters.html

Finding duplicates with SQL?

Suppose Col1 is the field name for which you want to find duplicates:

Select Col1, Count(Col1) as count
from table1
group by Col1
having Count(Col1) > 1

.

Formatting DateTime to Date in SQL

Select convert(varchar(10),GetDate(),101)

Output: 04/16/2009

Select convert(varchar(10),GetDate(),103)

Output: 16/04/2009

Rounding a number to 2 decimal places in SQL

Use T-SQL Convert Function.

Select convert ( decimal(8,2) , 9.4125 )

Output: 9.41

What is Windows Presentation Foundation (WPF)?

Windows Presentation Foundation (WPF) is a next-generation presentation system for building Windows client applications with visually stunning user experiences. With WPF, you can create a wide range of both standalone and browser-hosted applications. Some examples are Yahoo! Messenger and the New York Times Reader.

The core of WPF is a resolution-independent and vector-based rendering engine that is built to take advantage of modern graphics hardware. WPF extends the core with a comprehensive set of application-development features that include Extensible Application Markup Language (XAML), controls, data binding, layout, 2-D and 3-D graphics, animation, styles, templates, documents, media, text, and typography. WPF is included in the Microsoft .NET Framework, so you can build applications that incorporate other elements of the .NET Framework class library.

Reference: http://msdn.microsoft.com/en-us/library/aa970268.aspx

What is LINQ?