DATABASE | SQL SERVER | SQL SERVER INTERVIEW QUESTION AND ANSWERS 2 | WHAT ARE THE DIFFERENCE BETWEEN CLUSTERED AND A NON-CLUSTERED INDEX? | WHAT ARE THE SYSTEM DATABASE IN SQL SERVER 2008? | WHAT IS DENORMALIZATION AND WHEN WOULD YOU GO FOR IT? | WHAT ARE THE DIFFERENT TYPES OF SUB-QUERIES? | WHAT ARE CONSTRAINTS? EXPLAIN DIFFERENT TYPES OF CONSTRAINTS?

SQL Server Interview Question and Answers:

6.     What are the difference between clustered and a non-clustered index?
      A Clustered index is a special type of index that reorders the way in which each records in the table are physically stored.
A Non clustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows on disk.

7.     What are the System Database in Sql server 2008?
    Master
    Model
    Msdb
    Tempdb
    Resource

8.     What is denormalization and when would you go for it?
      Denormalization is the process of attempting to optimize the performance of a database by adding redundant data or by grouping data.Denormalization is the reverse process of normalization.

9.     What are the different types of Sub-Queries?
    Single row subquery
    Multiple row subquery
    Correralted row subquery

10.     What are constraints? Explain different types of constraints?
     Constraints is a rule or restriction concerning a piece of data that is enforced at the data level. A Constraint clause can constrain a single column or group of columns in a table.
    There are five types of Constraint namely

    Null / Not Null
    Primary Key
    Unique
    Check or Validation
    Foreign Key or References Key