SQL Server ->> 无法将数据库从SINGLE_USER模式切换回MULTI_USER模式（Error 5064）

报错信息如下：

Msg 5064, Level 16, State 1, Line 1
Changes to the state or options of database 'test' cannot be made at this time. The database is in single-user mode, and a user is currently connected to it.
Msg 5069, Level 16, State 1, Line 1
ALTER DATABASE statement failed. 

有人还连着数据库，从下面步骤检查：

1）通过sys.sysprocesses或者sys.dm_exec_sessions，或者存储过程sp_who，然后用KILL命令把会话切断

select * from sys.sysprocesses 
where spid > 50
And dbid=DB_ID ('MyDB')

SELECT * FROM sys.dm_exec_sessions
WHERE database_id = DB_ID ('MyDB')

2）如果上面还是行不通，再检查sys.dm_tran_locks，然后用KILL命令把会话切断

select * from sys.dm_tran_locks where resource_database_id= DB_ID ('MyDB')