An actual execution plan shows how SQL Server really ran a query, with the true row counts beside the estimates. This post gets the plan three ways, as a graphical plan, as text with SET STATISTICS PROFILE and as XML, and uses a demo table to show how the estimate and the actual number can disagree.
Rows Read Per Thread: Four Ways to See Them in SQL Server
Rows read per thread show whether a parallel query shares its work evenly. The post shows two plan based methods, a T-SQL query over the last actual plan, and a live DMV for running queries. A 500,000 row demo proves the threads add up to the table.
Unique Index Performance: What a UNIQUE Index Saves
Unique index performance gains come from what the optimizer learns, not from smaller pages. A tested demo compares pages, reads, plans and CPU for a plain index and a unique index. It also shows the error a duplicate causes.
Trivial Plan: Why Some Queries Skip Full Optimization
Identify a trivial plan in SSMS and cached XML, understand skipped optimizer work, and compare a more complex query without forcing it.
Removing a Bad Plan From Cache Without Clearing Everything
Remove one bad plan from cache by handle, compare narrower recompilation choices, and fix the cause so the plan stays healthy.
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.
Maximize Execution Plan Space in SSMS With Two Settings
To maximize execution plan space in SSMS, send the results to their own tab and switch to full screen mode. This post lists the two settings, the shortcuts that go with them and the zoom controls for a large plan on a small screen.