Performance tuning mistakes are habits, and each one has a check. Eleven sit in one table, and five are measured on a demo database: a missing index, stale statistics, a row by row loop, a giant delete and a type that cannot be indexed.
SQL Server emergency? Email pinal@sqlauthority.com with URGENT in the subject line.
Updatable Ledger Tables: Proving No One Quietly Changed a Row
Update a row in a ledger table and the old version stays. Then verify the history with a digest, and break the digest to see what failure looks like.
Cold Cache vs Warm Cache: Testing Query Speed Fairly
Compare cold cache and warm cache query tests using isolated buffer clearing, logical and physical reads, and controlled measurements.
Turning Per-Second Counters Into Real Rates From DMVs
That per-second counter on your dashboard is probably a running total. Here is how to turn it into a real rate with two samples.
TRY_CAST vs CAST: Finding Rows That Will Not Convert Before a Load
Find text values that will not convert before loading, separate invalid and missing input, and use explicit date styles and culture parsing.
INSERT EXEC: Capturing a Procedure’s Result Set and Its Limits
Capture rows with INSERT EXEC, match result columns, understand nested and multiple-result limits, and choose supported alternatives.
Approximate Percentiles With APPROX_PERCENTILE_CONT
Use APPROX_PERCENTILE_CONT for large response-time summaries, compare exact percentiles, and interpret the documented rank error bound.
SQL Server slow? Let's fix it together in about four hours.
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