Where SQL Server Actually Store Data

SQL server by default stores the data in the files with extensions .MDF and .LDF under the path 
"C:\Program Files\Microsoft SQL Server\MSSQL\Data\"

What are the Global Temporary Tables

We can create global temporary tables but these are not using much in sql an the name of these table start with two pound signs. For example, ##interviewqsn is a global temporary table.As the name suggest these table is Global temporary tables and visible to all SQL Server connections. When we create any one of these all users can see it.

How can you raise custom errors from stored procedure ?

The RAISERROR statement is used to produce an ad hoc error message or to retrieve a
custom message that is stored in the sysmessages table. You can use this statement with
the error handling code presented in the previous section to implement custom error

How can you increase SQL performance ?

Following are tips which will increase your SQl performance :-


√ Every index increases the time in takes to perform INSERTS, UPDATES and
DELETES, so the number of indexes should not be very much. Try to use
maximum 4-5 indexes on one table, not more. If you have read-only table,
then the number of indexes may be increased.

What are different types of joins and whats the difference between them ?

INNER JOIN
Inner join shows matches only when they exist in both tables.Example in the below SQL
there are two tables Customers and Orders and the inner join in made on Customers

What is normalization? What are different type of normalization?

It is set of rules that has been established to aid in the design of tables that are meant to
be connected through relationships. This set of rules is known as Normalization.