SQL Interview Questions

sony · 24-01-2010, 03:54 PM

Guys, let's share some important SQL Interview Questions.

imtiaz · 25-01-2010, 06:29 AM

"Where" is a kind of restriction statement. You use where clause to restrict all the data from DB. Where clause is using before result retrieving. But Having clause is using after retrieving the data. Having clause is a kind of filtering command.

imtiaz · 25-01-2010, 06:32 AM

What is "normalization"? Why do you sometimes want to denormalize?

Normalizing data means eliminating redundant information from a table and organizing the data so that future changes to the table are easier. Denormalization means allowing redundancy in a table. The main benefit of denormalization is improved performance with simplified data retrieval and manipulation. This is done by reduction in the number of joins needed for data processing.

24-01-2010, 03:54 PM	#1
sony Member Join Date: Jan 2010 Posts: 243 Rep Power: 16	SQL Interview Questions Guys, let's share some important SQL Interview Questions.

25-01-2010, 06:29 AM	#2
imtiaz Member Join Date: Dec 2009 Posts: 57 Rep Power: 15	What is the difference between a "where" clause and a "having" clause? "Where" is a kind of restriction statement. You use where clause to restrict all the data from DB. Where clause is using before result retrieving. But Having clause is using after retrieving the data. Having clause is a kind of filtering command.

25-01-2010, 06:32 AM	#3
imtiaz Member Join Date: Dec 2009 Posts: 57 Rep Power: 15	What is "normalization"? What is "normalization"? Why do you sometimes want to denormalize? Normalizing data means eliminating redundant information from a table and organizing the data so that future changes to the table are easier. Denormalization means allowing redundancy in a table. The main benefit of denormalization is improved performance with simplified data retrieval and manipulation. This is done by reduction in the number of joins needed for data processing.