What I'm looking to do is create grouped sequences for continuous date ranges. Take the following sample data:
Person|BeginDate |EndDate
A |1/1/2015 |1/31/2015
A |2/1/2015 |2/28/2015
A |4/1/2015 |4/30/2015
A |5/1/2015 |5/31/2015
B |1/1/2015 |1/30/2015
B |8/1/2015 |8/30/2015
B |9/1/2015 |9/30/2015
If BeginDate in the current row is >1 day from the EndDate in the previous row then increment the counter by 1, otherwise assign the counter's current value. The sequencing would look like :
Person|BeginDate |EndDate |Sequence
A |1/1/2015 |1/31/2015|1
A |2/1/2015 |2/28/2015|1
A |4/1/2015 |4/30/2015|2
A |5/1/2015 |5/31/2015|2
B |1/1/2015 |1/30/2015|1
B |8/1/2015 |8/30/2015|2
B |9/1/2015 |9/30/2015|2
Partitioned and reset for each person.
For your testing :
CREATE TABLE ##SequencingTest(
Person char(1)
,BeginDate date
,EndDate date)
INSERT INTO ##SequencingTest
VALUES
('A','1/1/2015','1/31/2015')
,('A','2/1/2015','2/28/2015')
,('A','4/1/2015','4/30/2015')
,('A','5/1/2015','5/31/2015')
,('B','1/1/2015','1/30/2015')
,('B','8/15/2015','8/31/2015')
,('B','9/1/2015','9/30/2015')
You can do this with lag() and then a cumulative sum:
select t.*,
sum(flag) over (partition by person order by begindate) as sequence
from (select t.*,
(case when datediff(day, lag(endDate) over (partition by person order by begindate), begindate) < 2
then 0
else 1
end) as flag
from t
) t;
If the continuous end dates are always 1 day before the next start date you could do something really primitive like this:
SELECT S1.Person, S1.BeginDate, S1.EndDate, SUM(S2.Cntr) AS Sequence
FROM Sequencing S1
INNER JOIN (SELECT Person, BeginDate,
CASE WHEN EXISTS (SELECT Person FROM Sequencing S2 WHERE S2.[EndDate] =
DATEADD(d, -1, S1.[BeginDate]) AND S2.Person = S1.Person) THEN 0 ELSE 1 END AS Cntr
FROM [Sequencing] S1
) S2
ON S1.Person = S2.Person
AND S1.BeginDate >= S2.BeginDate
GROUP BY S1.Person, S1.BeginDate, S1.EndDate
ORDER BY S1.Person, S1.BeginDate, S1.EndDate
Note I think you meant to say '1/31/2015' and '8/31/2015' as end dates to work with your example.
Also, #GordonLinoff's answer is probably better. I simply do not have the version of SQL Server to test it with.
Related
I'm working with a dataset that contains (among other columns) a userID and startDate. The goal is to have a new column "isRehire" that compares their startDate with previous startDates.
If the difference between startDates is within 1 year, isRehire = Y.
The difficulty and my issue comes in when there are more than 2 startDates for a user. If the difference between the 3rd and 1st startDate is over a year, the 3rd startDate would be the new "base date" for being a rehire.
userID
startDate
isRehire
123
07/24/19
N
123
02/04/20
Y
123
08/25/20
N
123
12/20/20
Y
123
06/15/21
Y
123
08/20/21
Y
123
08/30/21
N
In the above example you can see the issue visualized. The first startDate 07/24/19, the user is not a Rehire. The second startDate 02/04/20, they are a Rehire. The 3rd startDate 08/25/20 the user is not a rehire because it has been over 1 year since their initial startDate. This is the new "anchor" date.
The next 3 instances are all Y as they are within 1 year of the new "anchor" date of 08/25/20. The final startDate of 08/30/21 is over a year past 08/25/20, indicating a "N" and the "cycle" resets again with 08/30/21 as the new "anchor" date.
My goal is to utilize RANK OVER PARTITION to be able to complete this, as from my testing I believe there must be a way to assign ranks to the dates which can then be wrapped in a select statement for a CASE expression to be written. Although it's completely possible I'm barking up the wrong tree entirely.
Below you can see some of the code I've attempted to use to complete this, although without much success so far.
select TestRank,
startDate,
userID,
CASE WHEN TestRank = TestRank THEN (TestRank - 1
) ELSE '' END AS TestRank2
from
(
select userID,
startDate
RANK() OVER (PARTITION BY userID
ORDER BY startDate desc)
as TestRank
from [MyTable] a
WHERE a.userID = [int]
) b
This is complicated logic, and window functions are not sufficient. To solve this, you need iteration -- or in SQL-speak, a recursive CTE:
with t as (
select t.*, row_number() over (partition by id order by startdate) as seqnum
from mytable t
),
cte as (
select t.id, t.startdate, t.seqnum, 'N' as isrehire, t.startdate as anchordate
from t
where seqnum = 1
union all
select t.id, t.startdate, t.seqnum,
(case when t.startdate > dateadd(year, 1, cte.anchordate) then 'N' else 'Y' end),
(case when t.startdate > dateadd(year, 1, cte.anchordate) then t.startdate else cte.anchordate end)
from cte join
t
on t.seqnum = cte.seqnum + 1
)
select *
from cte
order by id, startdate;
Here is a db<>fiddle.
Help! We're trying to create a new column (Is Valid?) to reproduce the logic below.
It is a binary result that:
it is 1 if it is the first known value of an ID
it is 1 if it is 3 seconds or later than the previous "1" of that ID
Note 1: this is not the difference in seconds from the previous record
It is 0 if it is less than 3 seconds than the previous "1" of that ID
Note 2: there are many IDs in the data set
Note 3: original dataset has ID and Date
Attached a PoC of the data and the expected result.
You would have to do this using a recursive CTE, which is quite expensive:
with tt as (
select t.*, row_number() over (partition by id order by time) as seqnum
from t
),
recursive cte as (
select t.*, time as grp_start
from tt
where seqnum = 1
union all
select tt.*,
(case when tt.time < cte.grp_start + interval '3 second'
then tt.time
else tt.grp_start
end)
from cte join
tt
on tt.seqnum = cte.seqnum + 1
)
select cte.*,
(case when grp_start = lag(grp_start) over (partition by id order by time)
then 0 else 1
end) as isValid
from cte;
I'm not sure if this has been asked before because I'm having trouble even asking it myself. I think the best way to explain my dilemma is to use an example.
Say I've rated my happiness on a scale of 1-10 every day for 10 years and I have the results in a big table where I have a single date correspond to a single integer value of my happiness rating. I say, though, that I only care about my happiness over 60 day periods on average (this may seem weird but this is a simplified example). So I wrap up this information to a table where I now have a start date field, an end date field, and an average rating field where the start days are every day from the first day to the last over all 10 years, but the end dates are exactly 60 days later. To be clear, these 60 day periods are overlapping (one would share 59 days with the next one, 58 with the next, and so on).
Next I pick a threshold rating, say 5, where I want to categorize everything below it into a "bad" category and everything above into a "good" category. I could easily add another field and use a case structure to give every 60-day range a "good" or "bad" flag.
Then to sum it up, I want to display the total periods of "good" and "bad" from maximum beginning to maximum end date. This is where I'm stuck. I could group by the good/bad category and then just take min(start date) and max(end date), but then if, say, the ranges go from good to bad to good then to bad again, output would show overlapping ranges of good and bad. In the aforementioned situation, I would want to show four different ranges.
I realize this may seem clearer to me that it would to someone else so if you need clarification just ask.
Thank you
---EDIT---
Here's an example of what the before would look like:
StartDate| EndDate| MoodRating
------------+------------+------------
1/1/1991 |3/1/1991 | 7
1/2/1991 |3/2/1991 | 7
1/3/1991 |3/3/1991 | 4
1/4/1991 |3/4/1991 | 4
1/5/1991 |3/5/1991 | 7
1/6/1991 |3/6/1991 | 7
1/7/1991 |3/7/1991 | 4
1/8/1991 |3/8/1991 | 4
1/9/1991 |3/9/1991 | 4
And the after:
MinStart| MaxEnd | Good/Bad
-----------+------------+----------
1/1/1991|3/2/1991 |good
1/3/1991|3/4/1991 |bad
1/5/1991|3/6/1991 |good
1/7/1991|3/9/1991 |bad
Currently my query with the group by rating would show:
MinStart| MaxEnd | Good/Bad
-----------+------------+----------
1/1/1991|3/6/1991 |good
1/3/1991|3/9/1991 |bad
This is something along the lines of
select min(StartDate), max(EndDate), Good_Bad
from sourcetable
group by Good_Bad
While Jason A Long's answer may be correct - I can't read it or figure it out, so I figured I would post my own answer. Assuming that this isn't a process that you're going to be constantly running, the CURSOR's performance hit shouldn't matter. But (at least to me) this solution is very readable and can be easily modified.
In a nutshell - we insert the first record from your source table into our results table. Next, we grab the next record and see if the mood score is the same as the previous record. If it is, we simply update the previous record's end date with the current record's end date (extending the range). If not, we insert a new record. Rinse, repeat. Simple.
Here is your setup and some sample data:
DECLARE #MoodRanges TABLE (StartDate DATE, EndDate DATE, MoodRating int)
INSERT INTO #MoodRanges
VALUES
('1/1/1991','3/1/1991', 7),
('1/2/1991','3/2/1991', 7),
('1/3/1991','3/3/1991', 4),
('1/4/1991','3/4/1991', 4),
('1/5/1991','3/5/1991', 7),
('1/6/1991','3/6/1991', 7),
('1/7/1991','3/7/1991', 4),
('1/8/1991','3/8/1991', 4),
('1/9/1991','3/9/1991', 4)
Next, we can create a table to store our results, as well as some variable placeholders for our cursor:
DECLARE #MoodResults TABLE(ID INT IDENTITY(1, 1), StartDate DATE, EndDate DATE, MoodScore varchar(50))
DECLARE #CurrentStartDate DATE, #CurrentEndDate DATE, #CurrentMoodScore INT,
#PreviousStartDate DATE, #PreviousEndDate DATE, #PreviousMoodScore INT
Now we put all of the sample data into our CURSOR:
DECLARE MoodCursor CURSOR FOR
SELECT StartDate, EndDate, MoodRating
FROM #MoodRanges
OPEN MoodCursor
FETCH NEXT FROM MoodCursor INTO #CurrentStartDate, #CurrentEndDate, #CurrentMoodScore
WHILE ##FETCH_STATUS = 0
BEGIN
IF #PreviousStartDate IS NOT NULL
BEGIN
IF (#PreviousMoodScore >= 5 AND #CurrentMoodScore >= 5)
OR (#PreviousMoodScore < 5 AND #CurrentMoodScore < 5)
BEGIN
UPDATE #MoodResults
SET EndDate = #CurrentEndDate
WHERE ID = (SELECT MAX(ID) FROM #MoodResults)
END
ELSE
BEGIN
INSERT INTO
#MoodResults
VALUES
(#CurrentStartDate, #CurrentEndDate, CASE WHEN #CurrentMoodScore >= 5 THEN 'GOOD' ELSE 'BAD' END)
END
END
ELSE
BEGIN
INSERT INTO
#MoodResults
VALUES
(#CurrentStartDate, #CurrentEndDate, CASE WHEN #CurrentMoodScore >= 5 THEN 'GOOD' ELSE 'BAD' END)
END
SET #PreviousStartDate = #CurrentStartDate
SET #PreviousEndDate = #CurrentEndDate
SET #PreviousMoodScore = #CurrentMoodScore
FETCH NEXT FROM MoodCursor INTO #CurrentStartDate, #CurrentEndDate, #CurrentMoodScore
END
CLOSE MoodCursor
DEALLOCATE MoodCursor
And here are the results:
SELECT * FROM #MoodResults
ID StartDate EndDate MoodScore
----------- ---------- ---------- --------------------------------------------------
1 1991-01-01 1991-03-02 GOOD
2 1991-01-03 1991-03-04 BAD
3 1991-01-05 1991-03-06 GOOD
4 1991-01-07 1991-03-09 BAD
Is this what you're looking for?
IF OBJECT_ID('tempdb..#MyDailyMood', 'U') IS NOT NULL
DROP TABLE #MyDailyMood;
CREATE TABLE #MyDailyMood (
TheDate DATE NOT NULL,
MoodLevel INT NOT NULL
);
WITH
cte_n1 (n) AS (SELECT 1 FROM (VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) n (n)),
cte_n2 (n) AS (SELECT 1 FROM cte_n1 a CROSS JOIN cte_n1 b),
cte_n3 (n) AS (SELECT 1 FROM cte_n2 a CROSS JOIN cte_n2 b),
cte_Calendar (dt) AS (
SELECT TOP (DATEDIFF(dd, '2007-01-01', '2017-01-01'))
DATEADD(dd, ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) - 1, '2007-01-01')
FROM
cte_n3 a CROSS JOIN cte_n3 b
)
INSERT #MyDailyMood (TheDate, MoodLevel)
SELECT
c.dt,
ABS(CHECKSUM(NEWID()) % 10) + 1
FROM
cte_Calendar c;
--==========================================================
WITH
cte_AddRN AS (
SELECT
*,
RN = ISNULL(NULLIF(ROW_NUMBER() OVER (ORDER BY mdm.TheDate) % 60, 0), 60)
FROM
#MyDailyMood mdm
),
cte_AssignGroups AS (
SELECT
*,
DateGroup = DENSE_RANK() OVER (PARTITION BY arn.RN ORDER BY arn.TheDate)
FROM
cte_AddRN arn
)
SELECT
BegOfRange = MIN(ag.TheDate),
EndOfRange = MAX(ag.TheDate),
AverageMoodLevel = AVG(ag.MoodLevel),
CASE WHEN AVG(ag.MoodLevel) >= 5 THEN 'Good' ELSE 'Bad' END
FROM
cte_AssignGroups ag
GROUP BY
ag.DateGroup;
Post OP update solution...
WITH
cte_AddRN AS ( -- Add a row number to each row that resets to 1 ever 60 rows.
SELECT
*,
RN = ISNULL(NULLIF(ROW_NUMBER() OVER (ORDER BY mdm.TheDate) % 60, 0), 60)
FROM
#MyDailyMood mdm
),
cte_AssignGroups AS ( -- Use DENSE_RANK to create groups based on the RN added above.
-- How it works: RN set the row number 1 - 60 then repeats itself
-- but we dont want ever 60th row grouped together. We want blocks of 60 consecutive rows grouped together
-- DENSE_RANK accompolishes this by ranking within all the "1's", "2's"... and so on.
-- verify with the following query... SELECT * FROM cte_AssignGroups ag ORDER BY ag.TheDate
SELECT
*,
DateGroup = DENSE_RANK() OVER (PARTITION BY arn.RN ORDER BY arn.TheDate)
FROM
cte_AddRN arn
),
cte_AggRange AS ( -- This is just a straight forward aggregation/rollup. It produces the results similar to the sample data you posed in your edit.
SELECT
BegOfRange = MIN(ag.TheDate),
EndOfRange = MAX(ag.TheDate),
AverageMoodLevel = AVG(ag.MoodLevel),
GorB = CASE WHEN AVG(ag.MoodLevel) >= 5 THEN 'Good' ELSE 'Bad' END,
ag.DateGroup
FROM
cte_AssignGroups ag
GROUP BY
ag.DateGroup
),
cte_CompactGroup AS ( -- This time we're using dense rank to group all of the consecutive "Good" and "Bad" values so that they can be further aggregated below.
SELECT
ar.BegOfRange, ar.EndOfRange, ar.AverageMoodLevel, ar.GorB, ar.DateGroup,
DenseGroup = ar.DateGroup - DENSE_RANK() OVER (PARTITION BY ar.GorB ORDER BY ar.BegOfRange)
FROM
cte_AggRange ar
)
-- The final aggregation step...
SELECT
BegOfRange = MIN(cg.BegOfRange),
EndOfRange = MAX(cg.EndOfRange),
cg.GorB
FROM
cte_CompactGroup cg
GROUP BY
cg.DenseGroup,
cg.GorB
ORDER BY
BegOfRange;
I am trying to write SQL to calculate the start and end date from a single date called effective date for each item. Below is a idea of how my data looks. There are times when the last effective date for an item will be in the past so I want the end date for that to be a year from today. The other two items in the table example have effective dates in the future so no need to create and end date of a year from today.
I have tried a few ways but always run into bad data. Below is an example of my query and the bad results
select distinct tb1.itemid,tb1.EffectiveDate as startdate
, case
when dateadd(d,-1,tb2.EffectiveDate) < getdate()
or tb2.EffectiveDate is null
then getdate() +365
else dateadd(d,-1,tb2.EffectiveDate)
end as enddate
from #test tb1
left join #test as tb2 on (tb2.EffectiveDate > tb1.EffectiveDate
or tb2.effectivedate is null) and tb2.itemid = tb1.itemid
left join #test tb3 on (tb1.EffectiveDate < tb3.EffectiveDate
andtb3.EffectiveDate <tb2.EffectiveDate or tb2.effectivedate is null)
and tb1.itemid = tb3.itemid
left join #test tb4 on tb1.effectivedate = tb4.effectivedate \
and tb1.itemid = tb4.itemid
where tb1.itemID in (62741,62740, 65350)
Results - there is an extra line for 62740
Bad Results
I expect to see below since the first two items have a future end date no need to create an end date of today + 365 but the last one only has one effective date so we have to calculate the end date.
I think I've read your question correctly. If you could provide your expected output it would help a lot.
Test Data
CREATE TABLE #TestData (itemID int, EffectiveDate date)
INSERT INTO #TestData (itemID, EffectiveDate)
VALUES
(62741,'2016-06-25')
,(62741,'2016-06-04')
,(62740,'2016-07-09')
,(62740,'2016-06-25')
,(62740,'2016-06-04')
,(65350,'2016-05-28')
Query
SELECT
a.itemID
,MIN(a.EffectiveDate) StartDate
,MAX(CASE WHEN b.MaxDate > GETDATE() THEN b.MaxDate ELSE CONVERT(date,DATEADD(yy,1,GETDATE())) END) EndDate
FROM #TestData a
JOIN (SELECT itemID, MAX(EffectiveDate) MaxDate FROM #TestData GROUP BY itemID) b
ON a.itemID = b.itemID
GROUP BY a.itemID
Result
itemID StartDate EndDate
62740 2016-06-04 2016-07-09
62741 2016-06-04 2016-06-25
65350 2016-05-28 2017-06-24
This should do it:
SELECT itemid
,effective_date AS "Start"
,(SELECT MIN(effective_date)
FROM effective_date_tbl
WHERE effective_date > edt.effective_date
AND itemid = edt.itemid) AS "End"
FROM effective_date_tbl edt
WHERE effective_date <
(SELECT MAX(effective_date) FROM effective_date_tbl WHERE itemid = edt.itemid)
UNION ALL
SELECT itemid
,effective_date AS "Start"
,(SYSDATE + 365) AS "End"
FROM effective_date_tbl edt
WHERE 1 = ( SELECT COUNT(*) FROM effective_date_table WHERE itemid = edt.itemid )
ORDER BY 1, 2, 3;
I did this exercise for Items that have multiple EffectiveDate in the table
you can create this view
CREATE view [VW_TESTDATA]
AS ( SELECT * FROM
(SELECT ROW_NUMBER() OVER (ORDER BY Item,CONVERT(datetime,EffectiveDate,110)) AS ID, Item, DATA
FROM MyTable ) AS Q
)
so use a select to compare the same Item
select * from [VW_TESTDATA] as A inner join [VW_TESTDATA] as B on A.Item = B.Item and A.id = B.id-1
in this way you always minor and major Date
I did not understand how to handle dates with only one Item , but it seems the simplest thing and can be added to this query with a UNION ALL, because the view not cover individual Item
You also need to figure out how to deal with Item with two equal EffectiveDate
you should use the case when statement..
[wrong query because a misunderstand of the requirements]
SELECT
ItemID AS Item,
StartDate,
CASE WHEN EndDate < Sysdate THEN Sysdate + 365 ELSE EndDate END AS EndDate
FROM
(
SELECT tabStartDate.ItemID, tabStartDate.EffectiveDate AS StartDate, tabEndDate.EffectiveDate AS EndDate
FROM TableItems tabStartDate
JOIN TableItems tabEndDate on tabStartDate.ItemID = tabEndDate.ItemID
) TableDatesPerItem
WHERE StartDate < EndDate
update after clarifications in the OP and some comments
I found a solution quite portable, because it doesn't make use of partioning but endorses on a sort of indexing rule that make to correspond the dates of each item with others with the same id, in order of time's succession.
The portability is obviously related to the "difficult" part of query, while row numbering mechanism and conversion go adapted, but I think that it isn't a problem.
I sended a version for MySql that it can try on SQL Fiddle..
Table
CREATE TABLE ITEMS
(`ItemID` int, `EffectiveDate` Date);
INSERT INTO ITEMS
(`ItemID`, `EffectiveDate`)
VALUES
(62741, DATE(20160625)),
(62741, DATE(20160604)),
(62740, DATE(20160709)),
(62740, DATE(20160625)),
(62740, DATE(20160604)),
(62750, DATE(20160528))
;
Query
SELECT
RESULT.ItemID AS ItemID,
DATE_FORMAT(RESULT.StartDate,'%m/%d/%Y') AS StartDate,
CASE WHEN RESULT.EndDate < CURRENT_DATE
THEN DATE_FORMAT((CURRENT_DATE + INTERVAL 365 DAY),'%m/%d/%Y')
ELSE DATE_FORMAT(RESULT.EndDate,'%m/%d/%Y')
END AS EndDate
FROM
(
SELECT
tabStartDate.ItemID AS ItemID,
tabStartDate.StartDate AS StartDate,
tabEndDate.EndDate
,tabStartDate.IDX,
tabEndDate.IDX AS IDX2
FROM
(
SELECT
tabStartDateIDX.ItemID AS ItemID,
tabStartDateIDX.EffectiveDate AS StartDate,
#rownum:=#rownum+1 AS IDX
FROM ITEMS AS tabStartDateIDX
ORDER BY tabStartDateIDX.ItemID, tabStartDateIDX.EffectiveDate
)AS tabStartDate
JOIN
(
SELECT
tabEndDateIDX.ItemID AS ItemID,
tabEndDateIDX.EffectiveDate AS EndDate,
#rownum:=#rownum+1 AS IDX
FROM ITEMS AS tabEndDateIDX
ORDER BY tabEndDateIDX.ItemID, tabEndDateIDX.EffectiveDate
)AS tabEndDate
ON tabStartDate.ItemID = tabEndDate.ItemID AND (tabEndDate.IDX - tabStartDate.IDX = ((select count(*) from ITEMS)+1) )
,(SELECT #rownum:=0) r
UNION
(
SELECT
tabStartDateSingleItem.ItemID AS ItemID,
tabStartDateSingleItem.EffectiveDate AS StartDate,
tabStartDateSingleItem.EffectiveDate AS EndDate
,0 AS IDX,0 AS IDX2
FROM ITEMS AS tabStartDateSingleItem
Group By tabStartDateSingleItem.ItemID
HAVING Count(tabStartDateSingleItem.ItemID) = 1
)
) AS RESULT
;
everyone. I can't do the following query. Please help.
Initial data and ouput are on the following excel initial data/output google/drive
Here is the logic: for 'Rest' = 2500, it takes minimum value of 'Date', increments it by one and put it into Date1 column of output; Date2 receives the minimum value of date of the next 'Rest' value (1181,85).. and so on: Date1 receives 'Rest' (1181,85) min value of 'Date'(14.01.2013) incremented by one (15.01.2013) and so on. It should not do the above operations for 'Rest' value of zero (it should just skip it). We can't initially delete rows with 'Rest' value of zero, because their Date is used in Date2, as I have explained above. There are many 'accNumber's, it should list all of them. Please help. I hope you understood, if not ask for more details. Thanks in advance. I'm using SQL server.
If I've understood you correctly, you want to group the items by rest number, and then display the minimum date + 1 day, as well as the minimum date for the "next" rest number. What are you expecting to happen when the Rest number is 0 in two different places?
with Base as
(
select t.AccNum,
t.Rest,
DATEADD(day, 1, MIN(t.Date)) as [StartDate],
ROW_NUMBER() OVER (ORDER BY MIN(t.Date)) as RowNumber
from Accounts t
where t.Rest <> 0
group by t.AccNum, t.Rest
)
select a.AccNum, a.Rest, a.StartDate, DATEADD(DAY, -1, b.StartDate) as [EndDate]
from Base a
left join Base b
on a.RowNumber = b.RowNumber - 1
order by a.[StartDate]
If there's the possibility of the Rest number being duplicated further down, but that needing to be a separate item, then we need to be a bit cleverer in our initial select query.
with Base as
(
select b.AccNum, b.Rest, MIN(DATEADD(day, 1, b.Date)) as [StartDate], ROW_NUMBER() OVER (ORDER BY MIN(Date)) as [RowNumber]
from (
select *, ROW_NUMBER() OVER (PARTITION BY Rest ORDER BY Date) - ROW_NUMBER() OVER (ORDER BY Date) as [Order]
from Accounts a
-- where a.Rest <> 0
-- If we're still filtering out Rest 0 uncomment the above line
) b
group by [order], AccNum, Rest
)
select a.RowNumber, a.AccNum, a.Rest, a.StartDate, DATEADD(DAY, -1, b.StartDate) as [EndDate]
from Base a
left join Base b
on a.RowNumber = b.RowNumber - 1
order by a.[StartDate]
Results for both queries:
Account Number REST Start Date End Date
45817840200000057948 2500 2013-01-01 2013-01-14
45817840200000057948 1181 2013-01-15 2013-01-31
45817840200000057948 2431 2013-02-01 2013-02-09
45817840200000057948 1563 2013-02-10 NULL