Record Set,Index,Denormilization

1. Which clause is used to sort the records in the result set? 
2. Which it the major disadvantage of creating and using index? 
3. What are advantages and disadvantages of DE-normalization? 

1. The ORDER BY clause allows you to sort the records in your result set. 
2. They increase the disk space requirements of your database. 
3. Performance is improved by denormalization, but requires more extraneous efforts to keep track of related data.