Check login database access by matching the login SID against the users of every online database. One query shows the user, the CONNECT state and the guest back door, and it needs no impersonation.
Flush Authentication Cache: Who Can Run DBCC FLUSHAUTHCACHE
Flush authentication cache entries with DBCC FLUSHAUTHCACHE. This post tests the command on SQL Server 2025, shows who can run it and that on SQL Server 2025 it ends no open session, and says what it is documented to do on Azure SQL Database.
SQL SERVER – Fix Error – Cannot execute as the database principal because the principal “dbo” does not exist
One of my clients recently sent me an email with the following error. The error was visible in the error log and was about the database principal.
Max Server Memory Set Too Low: Fix It Through the DAC
Max server memory set too low can stop SQL Server from answering normal connections. This post shows how to connect through the Dedicated Administrator Connection, raise the value with sp_configure and start the service when it will not start.
distributor_admin Login: Why Renaming It Is a Bad Idea
Do not rename the distributor_admin login on a server that uses replication. This post shows how to check whether replication uses it, and a loopback demo with a throwaway login that shows what a rename breaks.
CLR Integration in SQL Server: When It Still Makes Sense
Review CLR integration uses, inventory existing assemblies, preserve strict security, and compare SQL Server 2025 built-in alternatives.
Deny Drop Permission for a Table in SQL Server
To deny drop permission for a table, deny ALTER on its schema, because DENY DELETE only stops row deletes. This post tests both on a demo database and shows what each deny blocks and what it leaves open.