How to: Change Server Authentication Mode
During installation, SQL Server Database Engine is set to either Windows Authentication mode or SQL Server and Windows Authentication mode. This topic describes how to change the security mode after installation.
If Windows Authentication mode is selected during installation, the sa login is disabled. If you later change authentication mode to SQL Server and Windows Authentication mode, the sa login remains disabled. To enable the sa login, use the ALTER LOGIN statement.
The sa account is a well-known SQL Server account and it is often targeted by malicious users. Do not enable the sa account unless your application requires it. It is very important that you use a strong password for the sa login.
The sa login can only connect to the server by using SQL Server Authentication.
To change security authentication mode
In SQL Server Management Studio Object Explorer, right-click the server, and then click Properties.
On the Security page, under Server authentication, select the new server authentication mode, and then click OK.
In the SQL Server Management Studio dialog box, click OK to acknowledge the requirement to restart SQL Server.
To restart SQL Server from SQL Server Management Studio
In Object Explorer, right-click your server, and then click Restart. If SQL Server Agent is running, it must also be restarted.
To enable the sa login by using Transact-SQL
Execute the following statements to enable the sa password and assign a password.
ALTER LOGIN sa ENABLE ; GO ALTER LOGIN sa WITH PASSWORD = '<enterStrongPasswordHere>' ; GO
To enable the sa login by using Management Studio
In Object Explorer, expand Security, expand Logins, right-click sa, and then click Properties.
On the General page, you might have to create and confirm a password for the sa login.
On the Status page, in the Login section, click Enabled, and then click OK.