I was asked a total of three questions on SQL and some questions on data warehousing

1. Find the skip - level manager of each employee
2. Find all books that are available in more than 50% of the languages? Optimize it use a single select statement
3. Find current month rank v/s previous month rank for each product based on sales.

DW :
Difference between MPP and SMP databases
Performance issues/optimization
Fact and Dimension tables