Q What is the purpose of UPDATE STATISTICS?

Updates information about the distribution of key values for one or more statistics groups (collections) in the specified table or indexed view.

Q What is the use of SCOPE_IDENTITY() function?

Returns the most recently created identity value for the tables in the current execution scope.

Q What are the different ways of moving data/databases between servers and databases in SQL Server?

There are lots of options available, you have to choose your option depending upon your requirements. Some of the options you have are: BACKUP/RESTORE, detaching and attaching databases, replication, DTS, BCP, logshipping, INSERT...SELECT, SELECT...INTO, creating INSERT scripts to generate data.

Q How do you transfer data from text file to database (other than DTS)?

Using the BCP (Bulk Copy Program) utility.

Q What's the difference between DELETE TABLE and TRUNCATE TABLE commands?

DELETE TABLE is a logged operation, so the deletion of each row gets logged in the transaction log, which makes it slow. TRUNCATE TABLE also deletes all the rows in a table, but it won't log the deletion of each row, instead it logs the deallocation of the data pages of the table, which makes it faster. Of course, TRUNCATE TABLE can be rolled back.