DBMS Basics Practice Test: Indexing and Hashing — Flashcards

Quiz questions on index definition, bitmap and ordered indices and various hashing techniques.

Indexing and hashing are two important concepts in database management systems (DBMS) that improve database efficiency. Indexing improves efficiency by reducing the number of disk accesses needed to process queries. Hashing determines the direct location of a data record on a disk without the use of an index structure. 

Indexing is used for rapid random lookups and efficient access of ordered records. It uses pre-organized data structures to speed up data retrieval, especially for range queries and ordered records. Some of the most commonly used indexing algorithms include:
B-tree indexing: Stores records in a sorted order, allowing the database to quickly iterate over the records in sorted order
Hash indexing: Maps each record in the table to a unique bucket based on its hash value, resulting in random order records in buckets 

Hashing is used to organize data into buckets that are easily searchable. It outperforms indexing when searching for specific items, especially in large databases. Hashing can also be used to ensure data integrity by implementing hash-based checksums. For example, hash functions such as MD5 or SHA-1 can verify if a record has been modified or tampered with. 

Here are some types of hashing:
Static hashing: The hash function always generates the same bucket's address
Dynamic hashing: Also known as extended hashing, this provides a mechanism in which data buckets are added and removed dynamically and on-demand