Difference between Session and Cookies

It is used to store user information in server memory. Usually it stores userid, name etc.. sensitive information stored in session and it will maintain its state when you navigate through a website.  You can store the session information either in cookies or cookieless mode.
If cookieless = false, session value stored in cookies, if it true it will be stored in the browser URL. but if you copy the URL and paste in another tab of  the same browser the session will be expired.

You can store the session in three modes
State server
SQL server

Session["userName"] = "Ganesh Ram";

if(Session["UserName"] != null)
  lblUserName.Text = Session["UserName"].ToString();
Cookies are stored per-user on the users machine. A cookie is usually just a bit of information. Cookies are usually used for simple user settings colours preferences etc. No sensitive information should ever be stored in a cookie.
You can never fully trust that a cookie has not been tampered with by a user or outside source however if security is a big concern and you must use cookies then you can either encrypt your cookies or set them to only be transmitted over SSL. A user can clear there cookies at any time or not allow cookies altogether so you cannot count on them being there just because I user has visited your site in the past.

//add a username Cookie
Response.Cookies["UserName"].Value = "Ganesh Ram";
Response.Cookies["UserName"].Expires = DateTime.Now.AddDays(10);

//request a username cookie
if(Request.Cookies["UserName"] != null)
   lblUserName.Text = Server.HtmlEncode(Request.Cookies["UserName"].Value);

Difference between Clustered index and Non-Clustered index

Indexing  is way to sort and search records in the table. It will improve the speed of locating and retrieval of records from the table

In SQL there are two types of index.
1. Clustered index
2. Non-Clustered index.

Clustered index is unique for any given table and we can have only one clustered index on a table. The leaf level of a clustered index is the actual data and the data is resorted in case of clustered index. 

Whereas in case of non-clustered index the leaf level is actually a pointer to the data in rows so we can have as many non-clustered indexes as we can on the db
In SQL 2005
Clustered index - 1 Clustered index
Non-Clustered index - 249 Non-Clustered index
In SQL 2008 
Clustered index - 1 Clustered index
Non-Clustered index - 999 Non-Clustered index 

USE Sample
Name nvarchar(150),
Address nvarchar(250),
Salary varchar(25) )

Define Stored procedure ?

It is a collection of transact sql statements that can take or return user supplied parameters.

Maximum size of stored procedure is 128 MB.

Difference between Having and Group By clause ?

Having Clause : To filter the rows from the grouped results

Group By : is used for grouping the operation.

Group by : Ccause  is used to group the output of the WHERE clause..

Define View ?

It is nothing but a virtual table that represent the data in one or more tables in a alternative way.

What is index ?

Index is a pointer in sql server to retrieve the data faster from database.

It’s a physical structure containing pointers to data.

Its created in existing tables to locate rows more quickly and efficiently.

Types of Index:

a)    Clustered Index : It contains only one index ie: Creating a primary key for the table.
Physical sorting of data in the storage media.

b)    Non-Clustered Index :  A table can contains 249 non-clustered index, It can be created outside of the database tables , that contain a sorted list of references to the table itself.

Define Delegates ?

Delegate is  a class that can hold reference to a method or a function .

Delegate class has a signature and it only reference those method whose signature is compliant with the class.

Delegates are type safe , secure , object oriented.