Q&A for those using, extending or developing Emacs
select convert(date, convert(varchar, datepart(year, P.CreationDate)) + '-' + convert(varchar, datepart(month, P.CreationDate)) + '-' + '01') monthYear, count(*) n from Posts P join PostTags PT on P.Id = PT.PostId join Tags T on PT.TagId = T.Id where T.TagName = 'c#' group by convert(date, convert(varchar, datepart(year, P.CreationDate)) + '-' + convert(varchar, datepart(month, P.CreationDate)) + '-' + '01')