What is the difference between a hash index and a B-tree?

A hash index and a B-tree are data structures used to speed up searches, but with different characteristics:

• Hash Index:

  • Uses a hash function for direct data access.
  • Excellent for exact key searches.
  • Does not support range searches or sorting.
  • Fast access (usually O(1)), but inefficient for partial matches.

• B-tree:

  • Self-balancing tree with multiple keys in a node.
  • Supports search, insert, delete in O(log n).
  • Efficient for range searches and sorting.
  • Used in databases and file systems.

Example: If you need to quickly find a record by an exact key — a hash index is better. If you need to select by a range of keys — a B-tree is preferable.