DBMS · Question 25 · Medium
A sparse (non-dense) index has an entry for only some of the search-key values. What does it require of the data file?
- The records must be sorted on the search key
- The file must have no duplicate records
- The file must be stored as a hash table
- The index must sit on a different disk from the file
Answer and explanation
Answer: A. The records must be sorted on the search key
Explanation: To find a record, you take the largest index entry not greater than the key and scan forward from there. That only works if the file is ordered on the search key, as with a primary (clustering) index.
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