SQL Query for Grouping the results based on sequence - sql

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
I want to group the continuous sequence numbers into a single row like this:
ID Start End TotalAmt
1 1 3 1500
1 5 5 500
2 10 11 1200
3 1 1 700
3 3 3 700
Please help to achieve this result.

Answer 1

WITH numbered AS (
SELECT
ID, Seq, Amt,
SeqGroup = ROW_NUMBER() OVER (PARTITION BY ID ORDER BY Seq) - Seq
FROM atable
)
SELECT
ID,
Start = MIN(Seq),
[End] = MAX(Seq),
TotalAmt = SUM(Amt)
FROM numbered
GROUP BY ID, SeqGroup
ORDER BY ID, Start
;

Answer 2

Well, there's perhaps a more elegant way to do this (something hints at me that there is), but here's an approach that will work if you're using a version of SQL Server that accepts common table expressions:
use Tempdb
go
create table [Test]
(
[id] int not null,
[Seq] int not null,
[Amt] int not null
)
insert into [Test] values
(1, 1, 500),
(1, 2, 500),
(1, 3, 500),
(1, 5, 500),
(2, 10, 600),
(2, 11, 600),
(3, 1, 700),
(3, 3, 700)
;with
lower_bound as (
select *
from Test
where not exists (
select *
from Test as t1
where t1.id = Test.id and t1.Seq = Test.Seq - 1
)
),
upper_bound as (
select *
from Test
where not exists (
select *
from Test as t1
where t1.id = Test.id and t1.Seq = Test.Seq + 1
)
),
bounds as (
select id, (select MAX(seq) from lower_bound where lower_bound.id = upper_bound.id and lower_bound.Seq <= upper_bound.Seq) as LBound, Seq as Ubound
from upper_bound
)
select Test.id, LBound As [Start], UBound As [End], SUM(Amt) As TotalAmt
from Test
join bounds
on Test.id = bounds.id
and Test.Seq between bounds.LBound and bounds.Ubound
group by Test.id, LBound, UBound
drop table [Test]

Answer 3

This seems to work nicely. #breakingRows will contain all rows that break the sequence of id and seq (i.e. if id changes or if seq is not 1 more than the previous seq). With that table you can select all rows of such a sequence within #temp. I must add however that performance will probably be not all that good because of all the subqueries but you'll need to test to be sure.
declare #temp table (id int, seq int, amt int)
insert into #temp select 1, 1, 500
insert into #temp select 1, 2, 500
insert into #temp select 1, 3, 500
insert into #temp select 1, 5, 500
insert into #temp select 2, 10, 600
insert into #temp select 2, 11, 600
insert into #temp select 3, 1, 700
insert into #temp select 3, 3, 700
declare #breakingRows table (ctr int identity(1,1), id int, seq int)
insert into #breakingRows(id, seq)
select id, seq
from #temp t1
where not exists
(select 1 from #temp t2 where t1.id = t2.id and t1.seq - 1 = t2.seq)
order by id, seq
select br.id, br.seq as start,
isnull ((select top 1 seq from #temp t2
where id < (select id from #breakingRows br2 where br.ctr = br2.ctr - 1) or
(id = (select id from #breakingRows br2 where br.ctr = br2.ctr - 1) and
seq < (select seq from #breakingRows br2 where br.ctr = br2.ctr - 1))
order by id desc, seq desc),
br.seq)
as [end],
(select SUM(amt) from #temp t1 where t1.id = br.id and
t1.seq <
isnull((select seq from #breakingRows br2 where br.ctr = br2.ctr - 1 and br.id = br2.id),
(select max(seq) + 1 from #temp)) and
t1.seq >= br.seq)
from #breakingRows br
order by id, seq

Answer 4

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

Answer 5

Try following query.
select id, min(seq), max(seq), sum(amt) from table group by id
OOps, sorry, it is wrong query as you need sequence

Answer 6

SELECT Id, MIN(Seq) as Start, MAX(Seq) as End, SUM(Amount) as Total
FROM (
SELECT t.*, Seq - ROW_NUMBER() OVER (PARTITION BY Id ORDER BY Seq) Rn
FROM [Table] t
) as T
GROUP BY Id, Rn
ORDER BY Id, MIN(Seq)