An index can reduce the Performance of SELECT Queries when it changes a particular plan unfavorably. Readers asked three follow-up questions.
Index Slows Down SELECT? What an Unused Index Costs You
An index slows down SELECT queries only in small ways when the plan never reads it. This post measures compile memory with twelve unused indexes, shows the plan change when a related index appears, and counts what every insert and update pays. The real bill arrives on writes.
When was Table Accessed Last By User? – Interview Question of the Week #226
When was a table accessed last by a user? When clients say a table is rarely used, I run this report to check before we create or drop indexes.
Columnstore Deleted Rows: When the Delete Bitmap Slows Scans
Inspect columnstore deleted rows, measure delete-bitmap overhead, and choose targeted REORGANIZE work before a heavier rebuild.
Binary Collations: Byte-Order Sorting and Exact String Matches
Learn how a binary collation changes SQL Server sorting, exact string comparisons, index access, and column metadata checks.
Indexed Computed Columns: Speeding Up Code You Cannot Change
Use indexed computed columns to help fixed vendor queries on UPPER or CAST, while checking determinism and required SET options.
Wide Update Plans: What Every Extra Index Costs a Write
Inspect wide update plans, compare index-maintenance work with narrow updates, and read per-index counters without misreading STATISTICS IO.