Hash Index

What
Hash based indexes are ones that use the hash data structure to perform the function of indexing. As per my definition, an index is a function that takes a value (or set of values) and returns the pages/tuples that match those values on the given fields.

Advantages

 * Very fast for selections

Disadvantages

 * Does not support range queries

Implementations

 * Static Hashing
 * Extendible Hashing