I am trying to find out the users that has logged into TFS 2015 Update 3 in last 6 months.
Solution using C#/ REST API is good, if not available is there a way to generate the report using SQL.
I have followed this:This. I think the Query is not compatible with TFS 2015 Update 3 database.
This is only possible if you don't clean up or archive the contents of the tbl_command in the TFS databases. By default these are cleaned up after 7 days (from the top of my head). The limit can be changed by altering the job definition (which may need to be redone after each service pack installation).
Or you can setup a custom job that copies the contents of tbl_command to a custom table/database for future reference.
Which leaves you to see whether a user has made any work item changes or checked in code in he last 6 months, queued any builds, triggered any releases... Each uses a different API and a lot of these don't offer a easy query by user interface as far as I can know.
来源：https://stackoverflow.com/questions/42810431/find-out-the-users-that-has-logged-in-to-tfs-in-last-6-months