SQL Query for Grouping the results based on sequence

Question

I have a table like this:

ID  Seq  Amt
1   1    500
1   2    500
1   3    500
1   5    500
2   10   600
2   11   600
3   1    700
3   3    700

Answer 1

Since Andriy has already posted the gold solution, here's my take using an UPDATE statement to get the result from a temp table, just for fun.

declare @tmp table (
    id int, seq int, amt money, start int, this int, total money,
    primary key clustered(id, seq))
;
insert @tmp
select *, start=seq, this=seq, total=convert(money,amt)
from btable
;
declare @id int, @seq int, @start int, @amt money
update @tmp
set 
    @amt = total = case when id = @id and seq = @seq+1 then @amt+total else amt end,
    @start = start = case when id = @id and seq = @seq+1 then @start else seq end,
    @seq = this = seq,
    @id = id = id
from @tmp
option (maxdop 1)
;
select id, start, max(this) [end], max(total) total
from @tmp
group by id, start
order by id, start

Notes:

• btable: your table name
• id int, seq int, amt money: expected columns in your table