Start profiling a table’s data with null counts, distinct values, lengths, and generated checks that expose misleading column definitions.
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.
What is Faster, SUM or COUNT? – Interview Question of the Week #231
Question: What is Faster, SUM or COUNT? Answer: Both are the same. I was asked this question during my Comprehensive Database Performance Health Check.
Transient Error in Automatic Seeding: Availability Database Failed to Seed
A transient error stopped automatic seeding of an availability database. The ERRORLOG on the secondary showed Msg 4353 about conflicting file relocations. Renaming a logical file let the database seed.
Availability Group Restore Error When You Add a Database
The availability group restore error appears when automatic seeding and a manual restore both fill the same secondary. The post explains the cause, shows read-only checks for the seeding mode and the replica roles, and gives the fix with its undo.
COPY_ONLY Full Backup Size: What Differs Between Always On Replicas
A COPY_ONLY full backup of the same database can have a different size on the primary and the secondary replica of an Always On group. This post reads the log pages in the backup messages, shows them on a standalone database and explains how to compare backups fairly. It also covers what a restore needs.
PAGELATCH_UP Waits and Suspended Sessions: Find the Hot Page
PAGELATCH_UP waits mean that sessions queue for the same page in memory, and that page can be named. This post reads the waiting sessions, turns the resource into a database, a file and a page, and tells an allocation page from an ordinary one. It then lists the fixes for tempdb and for a user database.
DBCC FLUSHAUTHCACHE: Force Azure SQL to Re-authenticate
DBCC FLUSHAUTHCACHE clears the authentication cache of an Azure SQL database, so open connections must authenticate again. This post shows what a password change does to open sessions on SQL Server, why Azure SQL needs the extra command and how to list the sessions you want to end. It also covers the cautions that matter.
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.
What are the Different Types of SQL Server CHECKPOINT? – Interview Question of the Week #230
Question: What are the Different Types of SQL Server CHECKPOINT?
Answer: There are four different kinds of checkpoints in SQL Server.