Find which database uses the most CPU from cached query stats and plan attributes, then use Query Store for restart-safe history.
Find the Most Resource Intensive Queries in SQL Server
To find resource intensive queries, read sys.dm_exec_query_stats and rank the cached statements by reads, CPU or time. This post builds a small demo, ranks it two ways, and fixes the worst offender with one index. It also explains what the numbers can and cannot tell you.
Finding the Worst Query in Five Minutes With Query Store
Find the worst query with Query Store totals, compare CPU and duration over the last day, inspect plans, and choose the first tuning target.
PREEMPTIVE Wait Stats: Calls Outside SQL Server
PREEMPTIVE wait stats record the time a task spends in code outside SQL Server, such as a call into Windows. On Night 19 at the Clipboard Diner, Kit picks up the wall phone to town hall and steps off the kitchen’s schedule. Then two queries find the preemptive waits that matter on your server.
THREADPOOL Wait Stats: When Worker Threads Run Out
THREADPOOL wait stats mean a task is waiting for a worker thread because every worker is already busy. On Night 16 at the Clipboard Diner, every cook holds a ticket that can’t move, and nobody is free to take a new order. Then two queries show how close your server is to its worker limit, and how to get in when nobody else can.
SOS_SCHEDULER_YIELD Wait Stats: Reading CPU Pressure
SOS_SCHEDULER_YIELD wait stats count the moments a query gives up the CPU after its 4 ms turn and waits to get it back. On Night 8 at the Clipboard Diner, every cook steps on and off the burners all night. Learn when this wait is harmless, when it means CPU pressure, and how to find the queries that burn the most CPU.
Parallelism Wait Stats: Tuning MAXDOP and Cost Threshold
Parallelism wait stats drop when two settings fit your server: cost threshold for parallelism decides which queries go parallel, and MAXDOP decides how many threads they get. On Night 7 at the Clipboard Diner, Casey writes two house rules for big parties. Then the kitchen starts learning on its own, the way DOP feedback does in SQL Server 2025 Enterprise.