Post your complete Query .
I have created same table as Project_To_Done
and write this same query where i used Group By Clause .
SELECT name
,CONVERT (DATETIME, DATEADD(s, SUM(( DATEPART(hh, Timer) * 3600 )
+ ( DATEPART(mi, Timer) * 60 ) + DATEPART(ss, Timer)), 0)) AS total_time
FROM Project_To_Done where name = @name
Group by name
,