```Some sample exam 2 questions:

1. Briefly define the following terms:

3NF (Third Normal Form)

BCNF (Boyce-Codd Normal Form)

Functional dependency

Lossless join decomposition

Dependency preserving decomposition

2. For each of the following index methods describe
(1) How the index is represented
(2) Where data is stored in the index
(3) How the following operations are executed
searching the index for a key value
insert a key value in the index
deleting a key value from the index

The methods:

ISAM
B+ Trees
Static Hashing
Extendible Hashing
Linear Hashing

3. Give an algorithm for a two-way external merge sort.  How many passes would
your algorithm need for a file consisting of 87 pages?

4. Give an algorithm for a n-way external merge sort.  How many passes would
your algorithm need for a file consisting of 87 pages when you have 15
buffers?

5. If you have a selection operator

SELECT equality condition ( relation )

how would you perform the operation under the following conditions, and
what would be the estimated cost of your approach in disk I/Os.

- There is no index, data is unsorted
- There is a clustered tree index
- There is a hash index

How would your answer change if the condition were not an equality
condition?

If there is more than one index available, how do you choose which
mechanism(s) to use?

6. How is the projection operator implemented with sorting?  How about hashing?
What are the expected costs for these operations in terms of disk I/Os?

7. Give pseudo-code for the following join operations (you may assume the join
is performed on a single attribute with an equality condition).  Also give
the expected cost for each operation.

Simple Nested Loops Join

Index Nested Loops Join

Block Nested Loops Join

Sort-Merge Join

Hash-Join

8. What is meant by the term reduction factor?  How does it apply in query
evaluation?  Give at least two examples of reduction factors and how they
might affect a particular query.

9. System R only considers left deep plans.  Why is this?  Give an example of
a plan that is left deep and one that is not.

10. Give an example of an optimization that might be performed on a query

11. What are Armstrong's Axioms for reasoning with a set of functional
dependencies?  What is the closure of a set of FDs?  What is the
attribute closure of a set of attributes with respect to a set of FDs?

12. What do functional dependencies relate to the concept of redundancy in a
database? What is our main mechanism for combatting redundancy?  Give
an example.

13. What is the most important thing to consider when determining whether
to include an index in a database schema?  Discuss some issues that should
be considered for choosing to include a particular index?

14. Under what situation would you not decompose a relation that is in 3NF
into a set of relations in BCNF?  Discuss the factors that influence these
types of decisions.

15. What is discretionary access control?  Explain how discretionary access
control is implemented using GRANT and REVOKE commands.

16. What is mandatory access control?  How does it differ from discretionary
access control?

17. Define the term transaction.  What are some of the important characteristics
of transactions?

```