SQL Server connection errors have a different message for each cause. The tests here trigger seven of them against a local SQL Server 2025 instance, show what the client says, what the ERRORLOG records, and how to find the port an instance listens on.
Connecting to SQL Server From Linux
Connecting to SQL Server from Linux requires the right Microsoft ODBC packages, a Kerberos plan, and certificate trust that matches the server name.
SQL SERVER – Connecting to Server Using Windows Authentication by SQLCMD
Windows Authentication by SQLCMD uses the current Windows identity with -E. It does not need a Windows password in the command.
Diagnosing a Frozen Server With the Dedicated Admin Connection
The dedicated admin connection provides a narrow emergency path to a stalled SQL Server; prepare remote access and keep diagnostics light.
LocalDB: SQL Server on a Developer’s Laptop
LocalDB runs SQL Server Express engine features in a developer-friendly local process; learn how to start, connect, and recognize its limits.
The New Go-Based sqlcmd: What Changed
The Go-based sqlcmd adds modern commands and contexts, but ODBC sqlcmd scripts need flag, output, and exit-code tests before a swap.
Backing Up SQL Server Express Without Agent
Backing up SQL Server Express requires a BACKUP script, sqlcmd, Windows Task Scheduler, retention rules, and proof that restores work.