Issues in Index Selection (Contd.)
Multi-attribute search keys should be considered when a WHERE clause contains several conditions.
- If range selections are involved, order of attributes should be carefully chosen to match the range ordering.
When considering a join condition:
- Hash index on inner is very good for Index Nested Loops.
- Should be clustered if join column is not key for inner, and inner tuples need to be retrieved.
- Clustered B+ tree on join column(s) good for Sort-Merge.