Indexing Rules of Thumb :
- Index every primary key and most foreign keys in the database.
- Attributes frequently referenced in SQL WHERE clauses are potentially
good candidates for an index. - Use a B+tree index for both equality and range queries.
- Choose carefully one clustered index for each table.
- Avoid or remove redundant indexes.
- Add indexes only when absolutely necessary.
- Add or delete index columns for composite indexes to improve performance.
Do not alter primary key columns. - Use attributes for indexes with caution when they are frequently updated.
- Keep up index maintenance on a regular basis; drop indexes only when
they are clearly hurting performance. - Avoid extremes in index cardinality and value distribution.
- Covering indexes (index only) are useful, but often overused.
- Use bitmap indexes for high-volume data, especially in data warehouses.
Index Selection Decisions :
- Does this table require an index or not, and if so which search
key should I build an index on? - When do I need multi-attribute (composite) search keys, and
which ones should I choose? - Should I use a dense or sparse index?
- When can I use a covering index?
- Should I create a clustered index?
- Is an index still preferred when updates are taken into
account? What are the tradeoffs between queries and updates for each index chosen? - How do I know I made the right indexing choice?
-- <Physical Database Design >