Computer Science – 8.2 Database Management Systems (DBMS) | e-Consult

An index in a DBMS is a data structure that improves the speed of data retrieval operations. It's essentially a shortcut to locate specific data within a table. Instead of scanning the entire table (a full table scan), the DBMS can use the index to quickly find the rows that match the search criteria.

Indexes improve query performance by allowing the DBMS to locate relevant rows much faster. Common index types include B-tree indexes, which are particularly efficient for range queries and equality searches. When a query uses a WHERE clause with an indexed column, the DBMS can use the index to directly access the relevant rows, significantly reducing the time required to execute the query. This is especially beneficial for large tables.

However, using indexes also has potential drawbacks:

• Increased storage space: Indexes require additional storage space on the disk.
• Slower write operations: When data is inserted, updated, or deleted, the indexes also need to be updated, which can slow down write operations.
• Index maintenance overhead: The DBMS needs to maintain the indexes, which requires periodic maintenance.