Date closest to current date in SQL (prior dates or future dates) - sql

Question

I am running into a bit of an issue with finding out how to look for dates closest to the current date. I looked at this among others:
Get closest date to current date sql
I also looked here: https://bytes.com/topic/sql-server/answers/79502-get-closest-date
I am using MS SQL 2012 and there have been many questions asked about this, so I apologize for bringing it back up. I can't seem to get my query to work.
Basically I have a table as follows:
ITEMNMBR | MINDATE | MAXDATE | CLOSESTDATE
------------------------------------------------
123456 | 2017-10-15 | 2017-11-04 | NULL
654321 | 2017-09-29 | 2017-12-08 | NULL
The current date would be today, '2017-10-03'. We would find for item number '123456' the closest date of purchase is 2017-10-15. For item number '654321' the closest date of purchase is 2017-09-29 as that happened much more recently than how long it will take for the next purchase to take effect (hence I am looking at an absolute value of the difference between the dates). You'll have to forgive me, but the query I am including doesn't include the "CLOSESTDATE" column. I've included it there to let you know that any of my calculations have rendered that column NULL. So here's what I have:
--Lines commented below are not used in the current iteration of the query
--DECLARE #dt DATETIME
--SET #dt = GETDATE()
SELECT
I.ITEMNMBR,
MIN(PDATE1) AS MINDATE,
MAX(PDATE1) AS MAXDATE
FROM dbo.IV00101 I
LEFT OUTER JOIN
(SELECT P.[Item Number],
P.[Req Date] AS PDATE1
FROM dbo.Purchases P
WHERE ((P.[Document Status] = 'Open') AND
(P.[POStat] <> 'Closed') AND
(P.[POStat] <> 'Received')) AND P.[Req Date] >= DATEADD(d, -15,
DATEDIFF(d, 0, GETDATE()))
) AS P ON P.[Item Number]= I.ITEMNMBR
WHERE P.[Item Number] = '123456'
GROUP BY
I.ITEMNMBR
ORDER BY MINDATE DESC
When I run this query, I get the table I outlined previously, minus the "CLOSESTDATE" column. The "CLOSESTDATE" column is what I want to use to display what date of purchase is closest to TODAY. Basically, if a date of purchase happened three days ago and the next date of purchase is a month out, then I want to show the date of purchase from three days ago. Also, the query can be written without using a subquery, but I was using other calculations within the subquery prior to reverting back to the rather simplistic original query. Thus, the query can be written like this:
SELECT
I.ITEMNMBR,
MIN(P.[Req Date]) AS MINDATE,
MAX(P.[Req Date]) AS MAXDATE
FROM dbo.IV00101 I
LEFT OUTER JOIN
Purchases P ON P.[Item Number] = I.ITEMNMBR
WHERE P.[Item Number] = '123456' ((P.[Document Status] = 'Open') AND
(P.[POStat] <> 'Closed') AND
(P.[POStat] <> 'Received')) AND P.[Req Date] >= DATEADD(d, -15,
DATEDIFF(d, 0, GETDATE()))
GROUP BY
I.ITEMNMBR
ORDER BY MINDATE DESC
Lastly, as you can see, I have a date constraint for the past 15 days so that anything older than that won't show up at all.
Many thanks in advance!

Answer 1

I'm still not quite understanding your question, but I hope this gives you a start, you can try the rextester sample here
But what it looks like to me is you need a simple case statement:
select ITEMNMBR
,case when abs(datediff(day, MINDATE, convert(date,getdate()))) > abs(datediff(day, MAXDATE, convert(date,getdate()))) then 'MINDATE is greater' else 'MAXDATE is greater' end as ClosestDate
from myTable
Kindly let me know if you have any questions. I'd be happy to help.

Answer 2

I have taken your data and schema and made an approximation of what I believe your underlying data actually looks like. From that, your problem is actually very simple:
declare #t table(ItemNumber int, ReqDate datetime, DocumentStatus nvarchar(100), POStat nvarchar(100))
insert into #t values
(123456,'2017-10-15','Open','Not Closed')
,(123456,'2017-11-04','Open','Not Closed')
,(654321,'2017-09-29','Open','Not Closed')
,(654321,'2017-12-08','Open','Not Closed')
,(123456,'2017-10-11','Open','Closed')
,(123456,'2017-11-01','Closed','Not Closed')
,(654321,'2017-09-21','Closed','Not Closed')
,(654321,'2017-12-01','Open','Received');
select t.ItemNumber
,min(t.ReqDate) as MinDate
,max(t.ReqDate) as MaxDate
-- Find the difference in days for both Min and Max dates, converting to positive numbers where negative,
,case when abs(datediff(d,min(t.ReqDate),getdate())) < abs(datediff(d,max(t.ReqDate),getdate()))
then min(t.ReqDate) -- And then return the appropriate one.
else max(t.ReqDate)
end as ClosestDate
from #t t
where t.DocumentStatus = 'Open'
and t.POStat not in('Closed','Received')
and t.ReqDate >= dateadd(d,-15,cast(getdate() as date))
group by t.ItemNumber
order by MinDate desc;
Output:
+------------+-------------------------+-------------------------+-------------------------+
| ItemNumber | MinDate | MaxDate | ClosestDate |
+------------+-------------------------+-------------------------+-------------------------+
| 123456 | 2017-10-15 00:00:00.000 | 2017-11-04 00:00:00.000 | 2017-10-15 00:00:00.000 |
| 654321 | 2017-09-29 00:00:00.000 | 2017-12-08 00:00:00.000 | 2017-09-29 00:00:00.000 |
+------------+-------------------------+-------------------------+-------------------------+

Answer 3

Change the initial part of the query with this:
SELECT DISTINCT
I.ITEMNMBR,
MIN(PDATE1) AS MINDATE,
MAX(PDATE1) AS MAXDATE
IF(ABS(DATEDIFF(MIN(PDATE1)-SYSDATETIME())) >
ABS(DATEDIFF(MAX(PDATE1)-SYSDATETIME())),
MAX(PDATE1),MIN(PDATE1)) as CLOSESTDATE