Wednesday, December 19, 2012

C# and .NET interview question: -What is short circuiting in C#?

When developers get this .NET interview question many of them get stunned with the name.

Short circuiting occurs when you do logical operations like ‘AND’ and ‘OR’.

 “When we use short circuit operators only necessary evaluation is done rather than full evaluation.
Let me explain the above sentence with a proper example. Consider a simple “AND” condition code as shown below. Please note we have only one “&” operator in the below code.

if(Condition1 & Condition2)

In the above case “Condition2” will be evaluated even if “Condition1” is “false”. Now if you think logically it does not make sense to evaluate “Condition 2”, if “Condition 1” is false.It’s a AND condition right? , soif the first condition is false it means the complete ANDcondition is false and it makes no sense to evaluate “Condition2”.

There’s where we can use short circuit operator “&&”. For the below code “Condition 2” will be evaluated only when “Condition 1” is true.
if(Condition1 && Condition2)

The same applies for “OR” operation. For the below code (please note its only single pipe(“|”).)   “Condition2” will be evaluated even if “Condition1” is “true”. If you think logically we do not need to evaluate “Condition2” if “Condition1” is “true”.

if(Condition1 | Condition2)

So if we change the same to double pipe (“||”) i.e. implement short circuit operators as shown in the below code, “Condition2” will be evaluated only if “Condition1” is “false”.

if(Condition1 || Condition2)

Taken from the best selling interview question book .NETinterview question by Shivprasadkoirala 

Here’s an awesome video on concurrent generic collections in C#.

Thursday, December 13, 2012

C# and .NET interview question: - What are symmetric and asymmetric algorithms?

Simple but important .NET / c# interview question.

Symmetric and Asymmetric are encryption algorithms. In Symmetric we have one key which encrypts messages and the same key helps to decrypt the message. In Asymmetric there are two keys public key and private key. Public key helps to encrypt message and private keys helps to decrypt the message. Everyone has the public key but the private key is held only by the authorized authority


Taken from the best selling interview question book .NET interview question by Shivprasad koirala.

Saturday, December 8, 2012

What is BI Semantic model (BISM) in SQL Server 2012?

Some days back I was installing SQL Server 2012 enterprise service pack 1. During installation when I was running through the setup, it gave me two options (multi-dimensional and tabular) of how I want to install SQL Server analysis service. Below is the image captured while doing installation

At the first glance these options are clearly meant to specify how we want the model design for our analysis service.

Now the first option i.e. “MultiDimensional” was pretty clear as I have been using them right from SQL Server 2005 till today i.e. (Star schema or Snow flake).

After some googling and hunting I came to know about the second option. Let me throw some light on the same and then we will conclude what is BISM.

Now overall we have two kinds of database systems , one is OLTP system where the database design thought process is in terms of tables and normalization rules ( 1st normal form , second normal form and third normal form  database design ) are followed.

The second kinds of systems are OLAP system’s where we mostly design is in terms of fact tables and dimension tables. Cube which is a multi-dimensional view of data is created properly if you design your database as OLAP system.

So in simple words we need to create a DB with OLAP design to ensure that proper cubes structure is created.

Now some times or I will say many times it’s really not feasible to create different structures and then create cubes from them. It would be great if SSAS gives us some options where we can do analysis straight from normalized simple tables.

For instance take simple end users who use “power pivot”. It’s very difficult for them to make understand OLAP models like dimension and fact tables. But yes they do understand tables with rows and columns.  If you see Microsoft excel the format is in terms of tables which have rows and columns and these end users are comfortable with a tabular structure.

 Below is a simple image of how simple end user visualize data in excel i.e. tabular – rows and columns.

That’s where exactly the second option i.e. the “Tabular” mode comes in to picture.

So if we put in simple words BISM (Business intelligence semantic model) is a model which tries to serve simple users / programmers who are comfortable with tabular structure and also maintains professional OLAP models for corporate.

So BISM is a unifying name for both Multi-dimension and tabular models.  So if you are personal BI person who loves ADHOC analysis, you can use power pivot or SSAS tabular IDE to do analysis. And if you are person who is working on a corporate project then Multi-dimension model is more scalable and worth looking in to.

Just a last quick note this is also a favorite SQL Server interview question which is making rounds now a days when SQL Server 2012 topic is discussed.

With all due respect to my publisher I have taken the above answer from my book SQL Server interview questions and answers.

You can also see my blog which has some important for SQL Server interview questions on Colaesce. 

You can also see my video on Can views be updated (SQL Server interview questions) ?