Question

In which of the following cases would it make the most sense to use a hash index?

a. select * from album where email like '%t%';
b. select * from track where track id > 1 and track id < 15;
c. select * from artist where artist id < 10;
d. select * from playlist where playlist id

Answer 1

The best use of a hash index is in Option D, where the query is an exact match search for a 'playlist id'. Hash indexes provide swift access for such point queries but are not suitable for range.

Step-by-step explanation:

A hash index is most suitable for point queries, where you look for a record with a specific key value. Therefore, the case that would most benefit from a hash index is:

d. select * from playlist where playlist id

In this case (assuming the rest of the command is a value equals to 'playlist id'), the query is looking for a specific playlist id, which is an exact-match search. Hash indexes excel at these types of queries because they can directly map the key to the specific location in the database, providing very fast access.

Cases a, b, and c involve range-based or pattern-matching searches, which are not the strengths of a hash index. For those types of queries, a tree-based index, such as a B-tree, might be more efficient as they are designed to handle range and ordered searches.