SQL - Select values from a table based on dates using incrementing dates - sql

Question

I have a SQL table of dates (MM/DD format), targets, and levels, as such:
Date Target Level
10/2 1000 1
10/4 2000 1
10/7 2000 2
I want to use those dates as tiers, or checkpoints, for when to use the respective targets and levels. So, anything on or after those dates (until the next date) would use that target/level. Anything before the first date just uses the values from the first date.
I want to select a range of dates (a 5 week range of dates, with the start date and end date of the range being determined by the current day: 3 weeks back from today, to 2 weeks forward from today) and fill in the targets and levels accordingly, as such:
Date Target Level
10/1 1000 1
10/2 1000 1
10/3 1000 1
10/4 2000 1
10/5 2000 1
10/6 2000 1
10/7 2000 2
10/8 2000 2
...
11/5 2000 2
How do I go about:
Selecting the range of dates (as efficiently as possible)
Filling in the range of dates with the respective target/level from the appropriate date in my table?
Thank you.

Answer 1

You can do this using outer apply. The following creates a list of dates using a recursive CTE:
with d as (
select cast(getdate() as date) as dte
union all
select dateadd(day, -1, dte)
from d
where dte >= getdate() - 30
select d.dte, t.target, t.level
from d outer apply
(select top 1 t.*
from t
where d.dte >= t.dte
order by t.dte desc
);

Answer 2

you can use a CTE to generate your 'missing' dates, then use a CROSS APPLY to obtain the target and level that was last active (by querying the TOP 1 DESC where the date is on or before current date) - finally I introduced 'maximum date' as a variable
DECLARE #MAXD as DATETIME = '20161105';
WITH DATS AS (SELECT MIN([Date]) D FROM dbo.YourTab
UNION ALL
SELECT dateadd(day,1,D) FROM DATS WHERE D < #MAXD)
select DATS.D, CA.Target, CA.Level from DATS
CROSS APPLY
(SELECT TOP 1 Y.Target, Y.Level FROM YourTab Y
WHERE
Y.[Date] <= DATS.D
ORDER BY Y.Date DESC) CA
option (maxrecursion 0);
I made a bit of a change with dates to go back 3 and forward two weeks - also I switched to outer apply to handle no data in force
DECLARE #MIND as DATETIME = dateadd(week,-3,cast(getdate() as date));
DECLARE #MAXD as DATETIME = dateadd(week, 5,#MIND);
WITH DATS AS (SELECT #MIND D
UNION ALL
SELECT dateadd(day,1,D) FROM DATS WHERE D < #MAXD)
select DATS.D, CA.Target, CA.Level from DATS
OUTER APPLY
(SELECT TOP 1 Y.Target, Y.Level FROM YourTab Y WHERE Y.[Date] <= DATS.D ORDER BY Y.Date DESC) CA
ORDER BY DATS.D
option (maxrecursion 0);
Final change - if there is no earlier value for the date - take first future row
DECLARE #MIND as DATETIME = dateadd(week,-3,cast(getdate() as date));
DECLARE #MAXD as DATETIME = dateadd(week, 5,#MIND);
WITH DATS AS (SELECT #MIND D
UNION ALL
SELECT dateadd(day,1,D) FROM DATS WHERE D < #MAXD)
select DATS.D, COALESCE(CA.Target, MQ.Target) Target , COALESCE(CA.Level, MQ.Level) Level from DATS
OUTER APPLY
(SELECT TOP 1 Y.Target, Y.Level FROM YourTab Y WHERE Y.[Date] <= DATS.D ORDER BY Y.Date DESC) CA
OUTER APPLY
(
SELECT TOP 1 M.Target, M.Level FROM YourTab M ORDER BY M.[Date] ASC
) MQ
ORDER BY DATS.D
option (maxrecursion 0);

Answer 3

I don't know why you store dates as MM/DD but you need some conversion into right datatype. This could do a trick:
;WITH YourTable AS (
SELECT *
FROM (VALUES
('10/2', 1000, 1),
('10/4', 2000, 1),
('10/7', 2000, 2)
) as t([Date], [Target], [Level])
), dates_cte AS ( --this CTE is generating dates you need
SELECT DATEADD(week,-3,GETDATE()) as d --3 weeks back
UNION ALL
SELECT dateadd(day,1,d)
FROM dates_cte
WHERE d < DATEADD(week,2,GETDATE()) --2 weeks forward
)
SELECT REPLACE(CONVERT(nvarchar(5),d,101),'/0','/') as [Date],
COALESCE(t.[Target],t1.[Target]) [Target],
COALESCE(t.[Level],t1.[Level]) [Level]
FROM dates_cte dc
OUTER APPLY ( --Here we got PREVIOUS values
SELECT TOP 1 *
FROM YourTable
WHERE CONVERT(datetime,REPLACE([Date],'/','/0')+'/2016',101) <= dc.d
ORDER BY CONVERT(datetime,REPLACE([Date],'/','/0')+'/2016',101) DESC
) t
OUTER APPLY ( --Here we got NEXT values and use them if there is no PREV
SELECT TOP 1 *
FROM YourTable
WHERE CONVERT(datetime,REPLACE([Date],'/','/0')+'/2016',101) >= dc.d
ORDER BY CONVERT(datetime,REPLACE([Date],'/','/0')+'/2016',101) ASC
) t1
Output:
Date Target Level
10/5 2000 1
10/6 2000 1
10/7 2000 2
10/8 2000 2
10/9 2000 2
10/10 2000 2
10/11 2000 2
10/12 2000 2
...
11/9 2000 2
EDIT
With Categories:
;WITH YourTable AS (
SELECT *
FROM (VALUES
('10/2', 1000, 1, 'A'),
('10/4', 3000, 1, 'B'),
('10/7', 2000, 2, 'A')
) as t([Date], [Target], [Level], [Category])
), dates_cte AS (
SELECT DATEADD(week,-3,GETDATE()) as d
UNION ALL
SELECT dateadd(day,1,d)
FROM dates_cte
WHERE d < DATEADD(week,2,GETDATE())
)
SELECT REPLACE(CONVERT(nvarchar(5),d,101),'/0','/') as [Date],
COALESCE(t.[Target],t1.[Target]) [Target],
COALESCE(t.[Level],t1.[Level]) [Level],
c.Category
FROM dates_cte dc
CROSS JOIN (
SELECT DISTINCT Category
FROM YourTable
) c
OUTER APPLY (
SELECT TOP 1 *
FROM YourTable
WHERE CONVERT(datetime,REPLACE([Date],'/','/0')+'/2016',101) <= dc.d
AND c.Category = Category
ORDER BY CONVERT(datetime,REPLACE([Date],'/','/0')+'/2016',101) DESC
) t
OUTER APPLY (
SELECT TOP 1 *
FROM YourTable
WHERE CONVERT(datetime,REPLACE([Date],'/','/0')+'/2016',101) >= dc.d
AND c.Category = Category
ORDER BY CONVERT(datetime,REPLACE([Date],'/','/0')+'/2016',101) ASC
) t1
ORDER BY c.Category, d

Answer 4

Not sure if I'm over simplifying this, but:
select min(X.Date) Date_Range_Start, max(X.date) Date_Range_End
, V.<value_date>
, isnull(X.Target, 'Out of range') Target
, isnull(X.Level, 'Out of range') Level
from X --replace this with your table
left join <value_table> V --table with dates to be assessed
on V.<Date> between X.Date_Range_Start and X.Date_Range_End
group by Target, Level, V.<value_date>