I need to track uptime to manage a service level agreement (SLA). How can I determine how long a particular instance of SQL Server has been running?

SQL Server doesn't offer a built-in system function that will return this information, but uptime is easy to track if you know a little about SQL Server's internal workings. SQL Server uses several connections to manage its internal processes. The SPID=1 connection to SQL Server is always a system connection established when SQL S...