Sql query to overlay date/period overrides over default dates - sql

Question

Any ideas on building a Sql Server (2008) query that will give me say the "date specific prices for an item based on the default or override where exists".
So a Default table might look like this - columns Price, StartDate, EndDate (yyyy-M-d):
Default: $10, 2010-1-1, 2010-2-1
The Override table like this:
Override: $12, 2010-1-5, 2010-1-8
And the query would return:
Result: $10, 2010-1-1, 2010-1-4
$12, 2010-1-5, 2010-1-8
$10, 2010-1-9, 2010-2-1
Probably I'd wrap this in a stored proc or function and call it for a specific date range.

Answer 1

Soemthing like:
SELECT
D.Price, ISNULL(O.StartDate, D.StartDate), ISNULL(O.EndDate, D.EndDate)
FROM
Default D
LEFT JOIN
Override O ON D.Price= O.Price

Answer 2

The proper design will be to have only one table. You don't want the override table at all. Just keep everyhing in the single table - constrained by the date range. The query becomes much simpler as well.
Your table structure becomes
CREATE TABLE Rates
(ID INT NOT NULL,
Rate Decimal NOT NULL,
FromDate NOT NULL,
ToDate NOT NULL,
CONSTRAINT PK_RATES (ID,FromDate,ToDate))
Then the query becomes
SELECT Rate FROM Rates WHERE ID = #ID AND FromDate = (SELECT MAX(FromDate) FROM Rates WHERE ID = #ID AND FromDate <= #Date) AND ToDate = (SELECT MIN(ToDate) FROM Rates WHERE ID = #ID AND ToDate >=#Date)

Answer 3

I think you're going to have to do something like this (assuming that you want to keep the override dates separate, and that you want to avoid anything procedural):
define and populate a utility table, listing each individual date which could be relevant to you
construct a SELECT that "marks" each date from this utility table as either i) belonging to the override dates or ii) belonging to the default dates
group the results of this SELECT by date and "mark"
join these results back to the respective price info

Answer 4

A bit late, but was looking for a solution for similar problem and did not find an answer so tried to cook one up.
One solution can be to try to adjust the first set of data to fit in the second set, and in the last step we will union the two sets, the adjusted data with the overlay data.
So we need to adjust the default set and that will require several steps of work.
Assumptions:-
The Default periods don’t overlap on their self.
Overlap periods don’t overlap on their self.
The overlap data must have gaps that are more than one day, to ensure that any adjustments will not affect another overlay period; we will not lose the overlay values associated as we will get them back in the last step.
For default periods that are partially overlapped (the overlap is larger or equal to a default period)
If a period start date overlaps with any overlay period we will change the start date to the end of the overlap period plus one day
Default: |<-------- P1 ------>|
Overlap: |<-----------O1------>|
=================================================================
Output: |<-----P1 ---->|
If a period end date overlaps with any overlay period we will change the end date to the start of the overlap period minus one day
Default: |<-------- P1 ------>|
Overlap: |<-----------O1------>|
===================================================================
Output: |<--- P1 ---->|
Remove any default period if it’s completely covered by an overlap period
Default: |<--- P1 --->|
Overlap: |<--------O1------>|
===================================================================
Output: nothing
For default periods that are broken by overlapped periods(the overlap is smaller than the periods)
Get the first part (from the beginning of the period to the first overlap period)
Get the intermediate parts, and that is from the end of any overlapped period to the start of the next overlapped period.
Get the last part( from the last overlapped to the end of the period)
Default: |<---------------------------- P1 ------------------------------>|
Overlap: |<---O1--->| |<---O2-->| |<--O3->|
===================================================================
Output: |<-P1->| |<-P1->| |<-P1->| |<-P1->|
Finally merge the data and get the result
Over lapping types that we are considering
Default: |<---- P1 --->|
Overlap: |<-----------O1------>|
===================================================================
Output: |<---- P1 --->||<-----------O1------>|
Lets build the T-SQL
With [System] as (
Select 1 [RowNum],cast('Jan 01,2017' as date) [StartDate],dateadd(day,-1,cast('Feb 01,2017' as date)) [EndDate],0500 [Value] union all
Select 2 [RowNum],cast('Feb 01,2017' as date) [StartDate],dateadd(day,-1,cast('Mar 01,2017' as date)) [EndDate],0700 [Value] union all
Select 3 [RowNum],cast('Mar 01,2017' as date) [StartDate],dateadd(day,-1,cast('Apr 01,2017' as date)) [EndDate],0900 [Value] union all
Select 4 [RowNum],cast('Apr 01,2017' as date) [StartDate],dateadd(day,-1,cast('May 01,2017' as date)) [EndDate],0700 [Value] union all
Select 5 [RowNum],cast('May 01,2017' as date) [StartDate],dateadd(day,-1,cast('Jun 01,2017' as date)) [EndDate],0900 [Value] union all
Select 6 [RowNum],cast('Jun 01,2017' as date) [StartDate],dateadd(day,-1,cast('Jul 01,9999' as date)) [EndDate],1500 [Value]
),Overrides as (
Select 1 [RowNum],cast('Feb 12,2017' as date) [StartDate],cast('Mar 25,2017' as date) [EndDate],1 [Value] union all
Select 2 [RowNum],cast('Mar 28,2017' as date) [StartDate],cast('May 15,2017' as date) [EndDate],2 [Value] union all
Select 3 [RowNum],cast('May 18,2017' as date) [StartDate],cast('May 20,2017' as date) [EndDate],3 [Value] union all
Select 4 [RowNum],cast('Jun 05,2017' as date) [StartDate],cast('Jun 08,2017' as date) [EndDate],4 [Value] union all
Select 5 [RowNum],cast('Jun 09,2017' as date) [StartDate],cast('Jun 16,2017' as date) [EndDate],5 [Value] union all
Select 6 [RowNum],cast('Jun 17,2017' as date) [StartDate],cast('Jun 22,2017' as date) [EndDate],6 [Value] union all
Select 7 [RowNum],cast('Jun 23,2017' as date) [StartDate],cast('Jun 27,2017' as date) [EndDate],7 [Value]
),PrepareOverridePeriods as (--if override periods have no gabs betwwen we need to merge them
Select p1.StartDate, p1.EndDate
from Overrides p1
left join Overrides p2 on p1.StartDate = DATEADD(day,1,p2.EndDate)
where p2.StartDate is null
union all
select p1.StartDate,p2.EndDate
from PrepareOverridePeriods p1
inner join Overrides p2 on p1.EndDate = DATEADD(day,-1,p2.StartDate)
),OverridePeriods as (
select ROW_NUMBER() over (order by StartDate) [RowNum],StartDate,MAX(EndDate) as EndDate
from PrepareOverridePeriods group by StartDate
),AdjustedPeriods as (
select s.RowNum,'Adj.' [type]
,isnull(dateadd(day,1,ShiftRight.EndDate),s.StartDate) [StartDate]
,isnull(dateadd(day,-1,ShiftLeft.StartDate),s.EndDate) [EndDate]
,s.Value
from System s
left outer join OverridePeriods ShiftRight on s.StartDate between ShiftRight.StartDate and ShiftRight.EndDate
left outer join OverridePeriods ShiftLeft on s.EndDate between ShiftLeft.StartDate and ShiftLeft.EndDate
left outer join OverridePeriods RemovePeriod on s.StartDate between RemovePeriod.StartDate and RemovePeriod.EndDate and s.EndDate between RemovePeriod.StartDate and RemovePeriod.EndDate
where RemovePeriod.StartDate is null
),SmallOverrides as ( --TODO: change SystemCalculated to AdjustSystemCalculatedPeriods
select ROW_NUMBER() over (partition by s.RowNum order by o.StartDate ) [RowNum],
o.RowNum [OverrideRowNum],o.StartDate [OverrideStartDate],o.EndDate [OverrideEndDate],s.Value [Value]
,s.RowNum [SystemRowNum],s.StartDate [SystemStartDate],s.EndDate [SystemEndDate]
from OverridePeriods o
inner join AdjustedPeriods s on o.StartDate between s.StartDate and s.EndDate and o.EndDate between s.StartDate and s.EndDate
)
--,FirstAndLastParts as (
--select [SystemRowNum],[type]
-- ,case when [type]='First' then min([SystemStartDate]) else dateadd(day,1,max(OverrideEndDate)) end [StartDate]
-- ,case when [type]='First' then dateadd(day,-1,min(OverrideStartDate)) else max([SystemEndDate]) end [EndDate]
-- ,min(Value) [Value]
-- from (select *,'First' [type] from SmallOverrides o union all
-- select *,'Last' [type] from SmallOverrides o) data
-- group by [SystemRowNum],[type]
--)
,FirstParts as (
select [SystemRowNum],'First' [type]
,min([SystemStartDate]) [StartDate]
,dateadd(day,-1,min(OverrideStartDate)) [EndDate]
,min(Value) [Value]
from SmallOverrides
group by [SystemRowNum]
),LastParts as (
select [SystemRowNum],'Last' [type]
,dateadd(day,1,max(OverrideEndDate)) [StartDate]
,max([SystemEndDate]) [EndDate]
,min(Value) [Value]
from SmallOverrides
group by [SystemRowNum]
),IntermediatParts as (
select s.SystemRowNum [RowNum],'Inter.' [type]
,dateadd(day,1,s.OverrideEndDate) [StartDate]
,dateadd(day,-1,e.OverrideStartDate) [EndDate]
,s.Value
from SmallOverrides s
left outer join SmallOverrides e on e.SystemRowNum=s.SystemRowNum and s.RowNum+1=e.RowNum
where e.RowNum is not null --remove the first and lasts
),AdjustedPeriodsFiltered as (--remove blocks that are broken to smaller pieces
select s.*
from AdjustedPeriods s
left outer join OverridePeriods o on o.StartDate between s.StartDate and s.EndDate and o.EndDate between s.StartDate and s.EndDate
where o.StartDate is null
),AllParts as (
select * from IntermediatParts union all --order by SystemRowNum,OverrideStartDate
select * from FirstParts union all
select * from LastParts union all
select * from AdjustedPeriodsFiltered
),Merged as (
select [RowNum],[type] [Source],StartDate,EndDate,Value,'System' [RecordType] from AllParts
union all
select [RowNum],'override' [Source],StartDate,EndDate,Value,'Override' [RecordType] from Overrides
)
select * from Merged order by StartDate
Can we adjust the data set in a different way, well yes, another approach is to get all the expected values from the start and end dates for the default periods and the overlay periods, then reconstruct a new set of periods, link it to the default values, merge it with the overlay, and we got it.
The same assumptions and step are taken as below:-
With [System] as (
Select 1 [RowNum],cast('Jan 01,2017' as date) [StartDate],dateadd(day,-1,cast('Feb 01,2017' as date)) [EndDate],0500 [Value] union all
Select 2 [RowNum],cast('Feb 01,2017' as date) [StartDate],dateadd(day,-1,cast('Mar 01,2017' as date)) [EndDate],0700 [Value] union all
Select 3 [RowNum],cast('Mar 01,2017' as date) [StartDate],dateadd(day,-1,cast('Apr 01,2017' as date)) [EndDate],0900 [Value] union all
Select 4 [RowNum],cast('Apr 01,2017' as date) [StartDate],dateadd(day,-1,cast('May 01,2017' as date)) [EndDate],0700 [Value] union all
Select 5 [RowNum],cast('May 01,2017' as date) [StartDate],dateadd(day,-1,cast('Jun 01,2017' as date)) [EndDate],0900 [Value] union all
Select 6 [RowNum],cast('Jun 01,2017' as date) [StartDate],dateadd(day,-1,cast('Jul 01,9999' as date)) [EndDate],1500 [Value]
),Overrides as (
Select 1 [RowNum],cast('Feb 12,2017' as date) [StartDate],cast('Mar 25,2017' as date) [EndDate],1 [Value] union all
Select 2 [RowNum],cast('Mar 28,2017' as date) [StartDate],cast('May 15,2017' as date) [EndDate],2 [Value] union all
Select 3 [RowNum],cast('May 18,2017' as date) [StartDate],cast('May 20,2017' as date) [EndDate],3 [Value] union all
Select 4 [RowNum],cast('Jun 05,2017' as date) [StartDate],cast('Jun 08,2017' as date) [EndDate],4 [Value] union all
Select 5 [RowNum],cast('Jun 09,2017' as date) [StartDate],cast('Jun 16,2017' as date) [EndDate],5 [Value] union all
Select 6 [RowNum],cast('Jun 17,2017' as date) [StartDate],cast('Jun 22,2017' as date) [EndDate],6 [Value] union all
Select 7 [RowNum],cast('Jun 23,2017' as date) [StartDate],cast('Jun 27,2017' as date) [EndDate],7 [Value]
),PrepareOverridePeriods as (--if override periods have no gabs between we need to merge them
Select p1.StartDate, p1.EndDate
from Overrides p1
left join Overrides p2 on p1.StartDate = DATEADD(day,1,p2.EndDate)
where p2.StartDate is null
union all
select p1.StartDate,p2.EndDate
from PrepareOverridePeriods p1
inner join Overrides p2 on p1.EndDate = DATEADD(day,-1,p2.StartDate)
),OverridePeriods as (
select ROW_NUMBER() over (order by StartDate) [RowNum],StartDate,MAX(EndDate) as EndDate
from PrepareOverridePeriods group by StartDate
)
,AllDates as (
select ROW_NUMBER() over (order by [Date]) [RowNum],data.Date from (
select dateadd(day,-1,OverridePeriods.StartDate) [Date] from OverridePeriods union all
select dateadd(day,+1,OverridePeriods.EndDate) [Date] from OverridePeriods union all
select StartDate [Date] from [System] union all
select EndDate [Date] from [System] ) as data
)
,NewPeriods as (
select sy.RowNum, s.[Date] [StartDate],n.[Date] [EndDate] ,sy.Value
from AllDates s
left outer join AllDates n on n.RowNum=s.RowNum+1
left outer join OverridePeriods o on s.[Date] between o.StartDate and o.EndDate and n.[Date] between o.StartDate and o.EndDate
left outer join [System] sy on s.[Date] between sy.StartDate and sy.EndDate
where
s.RowNum % 2 =1 and o.StartDate is null--group it by 2 and remove overriden areas
)
,Merged2 as (
select [RowNum], StartDate,EndDate,Value,'System' [RecordType] from NewPeriods
union all
select [RowNum], StartDate,EndDate,Value,'Override' [RecordType] from Overrides
)
select * from Merged2 order by StartDate
Im sure there may be another way to achieve the result required with some recursive approach, but for now this works for me.
For a last step we can try to merge the results if the value is the same, but I dont think that was requested.