sql server - Average of Most Recent 100 SQL Database Entries -

select     dc_grp.dc_grp, dc_grpx.reqt_id,            avg(results.[var]) average, stdev(results.[var]) stddev results inner join... 

currently pulling of var fields out of results, need recent 100. how can call recent 100 within avg( ) call?

assuming have column define recent, can subquery:

select     dc_grp.dc_grp, dc_grpx.reqt_id,            avg(r.[var]) average, stdev(r.[var]) stddev (select top 100 * results order createdat desc) r inner join... 

this example assumes name of column createdat.