Reason: Server is in single user mode. Only one administrator can connect at this time

单击Start→All Programs→Microsoft SQL Server 2008→Configuration Tools→SQL Server Configuration Manager.

右键单击面板右边的SQL Server ,然后在下拉菜单中选择Properties ,在SQL Server Properties 界面上，单击Advanced 选项卡。删除“;-m”,如下图所示，保存，重启SQL Server。