Question

If an index entry appears for only some of the search key values in the file, it is called as ________

(a) Dense key

(b) Dense index

(c) Sparse key

(d) Sparse index

The question was asked in class test.

My question is taken from Ordered Indices topic in chapter Indexing and Hashing of RDBMS

Answer 1

Correct answer is (d) Sparse index

Easiest explanation: In a sparse index, an index entry appears for only some of the search key values. Sparse indices can be used only if the relation is stored in the sorted order of the search key i.e. if the index is a clustering index.