max(line) , max(title_code) , 
 sum(headcount) as Headcounts
 from #tmpA
 group by dept , sect  with rollup
 

sect            sect                           Headcounts  
--------------- -------------------- ---- ---- ----------- 
DA              S1                   Lb   T2   12
DA              S2                   Lb   T1   6
DA              total ( by Dept ) :  Lb   T2   18
DB              S1                   Lb   T1   3
DB              S2                   Lb   T1   6
DB              total ( by Dept ) :  Lb   T1   9
DC              S1                   La   T1   3
DC              S2                   Lb   T1   3
DC              total ( by Dept ) :  Lb   T1   6
Grant total  :                       Lb   T2   33