I need a way to group data based on previous rows - sql

Question

Let me try to explain this again.
This table has a record for each person for each day of the month. There are approx 20 fields in the table. If any of the fields change (other than the date fields), then I want to group those records. So, for example, if days 1, 2, & 3 are the same, then when I read in day 4 and notice that it is changed, I want to group days 1, 2, & 3 together with a begindate of day one, and an enddate of day 3...etc
Rownum ID BegDate EndDate Field1, Field2.... Field20
1 1 6/1/2017 6/1/2017 xxxx xxxx xxxxx
2 1 6/2/2017 6/2/2017 xxxx xxxx xxxxx
3 1 6/3/2017 6/3/2017 xxxx xxxx xxxxx
4 1 6/4/2017 6/4/2017 yyyy yyyy yyyy
5 1 6/5/2017 6/5/2017 yyyy yyyy yyyy
6 1 6/6/2017 6/6/2017 xxxx xxxx xxxxx
7 1 6/7/2017 6/7/2017 xxxx xxxx xxxxx
8 1 6/8/2017 6/8/2017 zzzz zzzz zzzz
....
So in the example data above, I would have a group with rows 1,2,3 then a group with rows 4,5 then a group with rows 6,7 then a group with 8...etc
ID BegDate EndDate Field1 Field2 ...... Field20 Sum
1 6/1/2017 6/3/2017 xxxx xxxx xxxxx 3
1 6/4/2017 6/5/2017 yyyy yyyy yyyy 2
1 6/6/2017 6/7/2017 xxxx xxxx xxxxx 2
1 6/8/2017 6/15/2017 zzzz zzzz zzzz 8
.....

Answer 1

As example. Create table:
create table t
(date_ datetime,
status varchar(1));
And add data
insert into t values ('2017-11-01','A');
insert into t values ('2017-11-02','A');
insert into t values ('2017-11-03','A');
insert into t values ('2017-11-04','B');
insert into t values ('2017-11-05','B');
insert into t values ('2017-11-06','B');
insert into t values ('2017-11-07','C');
insert into t values ('2017-11-08','C');
insert into t values ('2017-11-09','C');
insert into t values ('2017-11-10','C');
insert into t values ('2017-11-11','B');
insert into t values ('2017-11-12','B');
insert into t values ('2017-11-13','B');
insert into t values ('2017-11-14','B');
insert into t values ('2017-11-15','B');
And use this query
select min(date_start),
IFNULL(date_end,now()),
status
from
( select
t1.date_ date_start,
(select min(date_) from t t2 where t2.date_>t1.date_ and t2.status<>t1.status) - interval 1 day as 'date_end',
t1.status status
from t t1
) a
group by date_end,status
order by 1
http://sqlfiddle.com/#!9/96e27/11

Answer 2

You can do this with a difference of row numbers:
select ID, min(BegDate) as Begdate, max(EndDate) as max(EndDate),
Field1, Field2, ...... Field20,
datediff(day, min(BegDate), max(EndDate))
from (select t.*,
row_number() over (partition by id order by begdate) as seqnum,
row_number() over (partition by id, Field1, Field2, . . ., Field20 order by begdate) as seqnum_2
from t
) t
group by id, (seqnum - seqnum_2), Field1, Field2, . . . Field20 ;

Answer 3

try below query (with 2 extra fields - field1 and field2).
To handle you 20 fields add remaining column whereever you see field1,field2 with field1, field2, field3,......field20
create table #tmp (RowNum int, id int,begdate datetime,EndDate datetime, field1 varchar(10),field2 varchar(10))
insert into #tmp values(1,1,'2017-06-01','2017-06-01','xxxxx','xxxxx')
insert into #tmp values(2,1,'2017-06-02','2017-06-02','xxxxx','xxxxx')
insert into #tmp values(3,1,'2017-06-03','2017-06-03','xxxxx','xxxxx')
insert into #tmp values(4,1,'2017-06-04','2017-06-04','yyyyy','yyyyy')
insert into #tmp values(5,1,'2017-06-05','2017-06-05','yyyyy','yyyyy')
insert into #tmp values(6,1,'2017-06-06','2017-06-06','xxxxx','xxxxx')
insert into #tmp values(7,1,'2017-06-07','2017-06-07','xxxxx','xxxxx')
insert into #tmp values(8,1,'2017-06-08','2017-06-08','zzzzz','zzzzz')
insert into #tmp values(9,1,'2017-06-09','2017-06-09','zzzzz','zzzzz')
insert into #tmp values(10,1,'2017-06-10','2017-06-10','zzzzz','zzzzz')
insert into #tmp values(11,2,'2017-06-04','2017-06-04','yyyyy','yyyyy')
insert into #tmp values(12,2,'2017-06-05','2017-06-05','yyyyy','yyyyy')
insert into #tmp values(13,2,'2017-06-06','2017-06-06','xxxxx','xxxxx')
insert into #tmp values(14,2,'2017-06-07','2017-06-07','xxxxx','xxxxx')
insert into #tmp values(15,1,'2017-06-11','2017-06-11','xxxxx','xxxxx')
insert into #tmp values(16,1,'2017-06-12','2017-06-12','xxxxx','xxxxx')
insert into #tmp values(17,1,'2017-06-13','2017-06-13','zzzzz','xxxxx')
insert into #tmp values(18,1,'2017-06-14','2017-06-14','zzzzz','xxxxx')
insert into #tmp values(19,1,'2017-06-15','2017-06-15','yyyyy','xxxxx')
insert into #tmp values(20,1,'2017-06-16','2017-06-16','zzzzz','xxxxx')
select ID, min(BegDate) as Begdate, max(EndDate) as EndDate,
Field1,Field2, /*Add all other fields here*/
datediff(day, min(BegDate), max(EndDate))+1 As [Sum]
from(
select *,
row_number() over (partition by id order by begdate) as seqnum,
row_number() over (partition by id, Field1,field2 /*Add all other fields here*/ order by begdate) as seqnum_2
from #tmp
) t
group by id, (seqnum - seqnum_2), Field1,Field2 /*Add all other fields here*/
order by ID,Begdate
Drop table #tmp