index-strategies

| Clustered | Table data order | Primary access path, range scans | | Nonclustered | Separate structure | Specific query patterns | | Columnstore | Column-based storage | Analytics, aggregations | | Filtered | Partial index | Well-known subsets | | Covering | All columns needed | Avoiding key lookups |

| WHERE Col = value | Nonclustered on Col | | WHERE Col = v1 AND Col2 = v2 | Nonclustered on (Col, Col2) | | WHERE Col = v ORDER BY Col2 | Nonclustered on (Col, Col2) | | WHERE Col BETWEEN x AND y | Col as leftmost key | | SELECT WHERE Col = v | Clustered or covering NC | | Large aggregations | Columnstore | | Specific subset queries | Filtered index |

| < 5% | None needed | | 5-30% | REORGANIZE | | > 30% | REBUILD |