If your SQL Server has both SQL and Windows logins and you’re not sure why, you’re not alone. Many IT teams without a dedicated DBA bump into this sooner or later. And sometimes…things break just because someone checked the wrong box during setup.
Let’s break it down.
Two Login Types, Two Worlds
SQL Server supports two authentication modes:
Windows Authentication
- Uses your Active Directory account (individual or group) to connect.
- Most secure and manageable in domain environments.
- Passwords are handled by Windows, so no extra password to manage in SQL Server.
SQL Server Authentication
- Uses a separate username and password stored inside SQL Server.
- Necessary for non-domain users, apps, or services outside your network.
- Password policies are optional (and often ignored… oof).
Mixed Mode vs Windows-Only Mode
Your SQL Server can be set to:
- Windows-only Mode (no SQL logins allowed), or
- Mixed Mode (allows both types)
Most installs use Mixed Mode, even when they don’t need to because “that’s how it was installed,” or “some app needed a SQL login once.”
Tip: Use Windows authentication whenever possible. It’s integrated, auditable, and far more secure.
Common Pitfalls
- “sa” is enabled and still using the default password (Yes, we’ve seen this. More than once.)
- SQL logins don’t expire or require password complexity, unless you set that option.
- Orphaned users (exists in the database but not on the server).
- Confusion about who can access what—especially after domain changes or user departures.
The Bottom Line:
- Audit your logins and users regularly. Know what’s there.
- Disable “sa” or rename it.
- Use Windows logins/groups for real people whenever possible.
- Use SQL logins only when Windows auth isn’t an option and treat them like sensitive credentials.
Security breaches often start with a misconfigured login. A little attention now saves a lot of pain later.
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Thanks for reading!
–Kevin
