diagnose-slow-query

Triages a slow Azure SQL Database query into one of four causes before anyone touches an index or a service tier: volatile, duration swings across executions; blocked, waiting on another session; regressed, a worse plan replaced a good one; or growing, duration rises with data volume. Reads Query Store runtime stats, plan history and per-plan waits, and knows where AUTO capture mode silently drops the query asked about. Use when a query "used to be fast" or runs inconsistently: "this took a second yesterday and ten today", "sometimes it's fast and sometimes it isn't", "did last night's deployment make this slower". Ends in a diagnosis, not a fix: CPU, memory, IO and tier go to diagnose-resource-pressure, blocking and deadlocks to diagnose-blocking-and-deadlocks, the plan itself to read-execution-plan, a query Query Store missed to capture-with-extended-events.