sqlserver interview questions

1.What is difference between Clustered and Non Clustered index?

There are two Types of Index available in Sql Server:

1) Clustered Index
2) Non Clustered Index

Index is used for increase the performance application.
1) Clustered Index sequential order .primary key default clustered index. each table only once clustered index.

2) unique key default non clustered index. There 256 non clustered index in each table.


2.how to find duplicates in a table in sql server?

This query demonstrates usage of GROUP BY, HAVING, ORDER BY in one query and returns the results with duplicate column and its count in descending order.

SELECT YourColumn, COUNT(*) TotalCount
FROM YourTable
GROUP BY YourColumn
HAVING COUNT(*) > 1
ORDER BY COUNT(*) DESC