I have an existing @table
ID Date Val
1 2014-10-01 1
2 2014-10-02 1
3 2014-10-03 2
4 2014-10-04 2
5 2014-10-05 2
6 2014-10-06 1
7 2014-10-07 1
8 2014-10-08 1
9 2014-10-09 1
The Date sequence is of importance. I need to see the first and last date for each Val sequence:
How do I get SQL to return the min/max dates per sequence? I need to show : i.e.
1 2014-10-01 2014-10-02
2 2014-10-03 2014-10-05
1 2014-10-06 2014-10-09
I got this working with the help of other developers with 2012's LAG function, but I need to use 2008 please
Failed attempt:
select t.Val,MIN(t.date),MAX(tnext.date)
from @T t join
@T tnext
on t.id = tnext.id - 1 and
t.Val <> tnext.val
group by
t.val
Setup:
declare @T table(ID int,[Date] date,Val int)
Insert Into @T(ID,[Date],Val)
values
(1,'2014/10/01', 1),
(2,'2014/10/02', 1),
(3,'2014/10/03', 2),
(4,'2014/10/04', 2),
(5,'2014/10/05', 2),
(6,'2014/10/06', 1),
(7,'2014/10/07', 1),
(8,'2014/10/08', 1),
(9,'2014/10/09', 1)
I believe this query should work:
select
val,
start_date = min(date),
end_date = max(date)
from
(
select
val,
date,
grp = row_number() over (partition by val order by date)
- row_number() over (order by date)
from
@t
) x
group by
grp, val
order by
min(date)
The query above assumes that the dates are strictly sequential.