Questions from Database Systems

Q: List two reasons why null values might be introduced into a database

List two reasons why null values might be introduced into a database.

Q: Use the definition of functional dependency to argue that each of Armstrong’s

Use the definition of functional dependency to argue that each of Armstrong’s axioms (reflexivity, augmentation, and transitivity) is sound.

Q: The hash-join algorithm as described in Section 15.5

The hash-join algorithm as described in Section 15.5.5 computes the natural join of two relations. Describe how to extend the hash-join algorithm to compute the natural left outer join, the natural ri...

Q: Suppose you have to compute a sum(C) (r

Suppose you have to compute a sum(C) (r) as well as A, by sum(C) (r). Describe how to compute these together using a single sorting of r.

Q: Write pseudo code for an iterator that implements a version of the

Write pseudo code for an iterator that implements a version of the sort – merge algorithm where the result of the final merge is pipelined to its consumers. Your pseudo code must define the standard ite...

Q: Explain how to split the hybrid hash-join operator into sub

Explain how to split the hybrid hash-join operator into sub-operators to model pipelining. Also explain how this split is different from the split for a hash-join operator.

Q: Suppose you need to sort relation r using sort—merge and

Suppose you need to sort relation r using sort—merge and merge—join the result with an already sorted relation s. a. Describe how the sort operator is broken into sub operators to model the pipelining...

Q: Suppose that a B+-tree index on (dept. name

Suppose that a B+-tree index on (dept. name, building) is available on relation Depart mint. What would be the best way to handle the following selection? Σ (building

Q: Suppose you want to get answers to r ⋈ s sorted on

Suppose you want to get answers to r ⋈ s sorted on an attribute of r, and want only the top K answers for some relatively small K. Give a good way of evaluating the query: a. When the join is on a for...

Q: Consider a relation r (A, B, C), with

Consider a relation r (A, B, C), with an index on attribute A. Give an example of a query that can be answered by using the index only, without looking at the tuples in the relation. (Query plans that...