SQL Server Indexes

Indexes are the single biggest lever for SQL Server query performance. This skill covers finding missing indexes, maintaining existing ones, eliminating unused indexes, and designing effective covering indexes.

Require exact-target DBA review of server, database, schema, table and index before executing any proposal. Use least privilege (ALTER on the target table), check constraints, query hints and other dependencies, and test in staging with a recovery plan. Never automatically execute returned SQL. Capture index definitions before changes; budget locks, transaction log, disk/tempdb capacity and a maintenance window. Check ONLINE support for the edition and index type; online operations still take locks.

Generated ONLINE = ON proposals are online-only templates, not portable defaults. Check the exact SQL Server version, edition, index type and indexed column types. EngineEdition alone does not establish eligibility. Do not remove ONLINE = ON to retry an unsupported operation. Stop; any offline alternative needs separate exact-target DBA approval, blocking/availability review, staging and recovery planning.