What are duplicate and overlapping indexes?

Duplicate indexes have effectively the same key definition and often the same coverage. Overlapping indexes share substantial leading key structure or coverage but are not exact duplicates.

For example, indexes on (CustomerId) and (CustomerId, OrderDate) INCLUDE (TotalAmount) may overlap depending on workload.

Consolidating redundant indexes can reduce storage and modification cost, but do not drop an index based solely on similar column names. Compare key order, INCLUDE columns, uniqueness, filters, usage, and query plans.