select - Update table Data without using while loop in sql server 2005 -

in sql have table data below

id      type     amount        1      type1       2000     2      type1       1000      3      type2        500     4      type3       3000     5      type1       2000    6      type2        500         7      type3       5000     8      type1       1000     

and want datas in select statement below

id      type     amount      current    1      type1       2000         2000                 2      type1       1000         1000                  3      type2        500          500                  4      type3       3000         3000                  5      type1       2000         3000                   6      type2       -500            0                  7      type3       5000         2000 8      type1      -1000         4000  

and on means each type must have current total amount based on amount type , need dont have while loop because takes long time execute

for eg:  in type 1  id      amount      current  1      2000-add       2000                    2      1000-sub       1000                   3      2000-add       3000                    4      1000-add       4000                    

how it

i think query work:

select id,type,amount,(select sum(amount) mytable t1 t1.type=t2.type , t1.id<=t2.id) currenttotal mytable t2