| Windows Authentication Mode
When you connect through a Microsoft Windows® user account, MS SQL Server validates the account name and password using the information present in the Windows operating system.
Mixed Mode (Windows Authentication or MS SQL Server Authentication)
It allows you to connect using Windows Authentication or MS SQL Server Authentication. If you connect via Microsoft Windows® user account, you can use the trusted connections (connections validated by Windows) in either Windows Authentication Mode or Mixed Mode. MS SQL Server Authentication is provided for backward compatibility.
Blank Password (not recommended)
If you attempt to connect to an instance of MS SQL Server by providing a blank login name, the MS SQL Server uses the Windows Authentication. Additionally, if you connect to an instance of MS SQL Server configured for Windows Authentication Mode using a specific login, the login is ignored and the Windows Authentication is used. |
