Partition by to get the correct date - sql

Question

I would like to retrieve the oldest date under the FirstScanned Column. My issue is that a product can be registered again at some point as a new product, when this happens, I'd like the FirstScanned to be retrieve the oldest scanned date based on the newest scan on Location 1
In the following example I'm trying to retrieve the correct FirstScanned Date without success:
CREATE TABLE [dbo].[Products123](
[ID] [int] NOT NULL,
[GTIN] [varchar](50) NULL,
[LocationID] [int] NULL,
[UserID] [int] NULL,
[Created] [datetime] )
insert into Products123(ID, GTIN, LocationID, UserID, Created)
Values(1, '12345678910', 1, 3, '2017-06-30 14:58:07.693'), -- Location "1" is when products was registered/scanned for this first time
(2, '12345678910', 5, 3, '2017-06-30 15:25:12.287'), -- The product is scanned into a new location
(3, '12345678910', 17, 3, '2017-06-30 14:58:07.693'), -- The product is now scanned into the "end" location and is considered to be closed
(4, '12345678910', 1, 7, '2017-08-01 11:34:16.347'), -- A month later the same productID has been registered,
(5, '12345678910', 4, 7, '2017-08-01 11:36:16.460') -- etc
DECLARE #Prev8workingdays date = CASE
WHEN datepart(dw, getdate()) IN (2,3,4) THEN dateadd(day,-14, getdate())
WHEN datepart(dw, getdate()) IN (1) THEN dateadd(day,-13, getdate())
ELSE dateadd(day,-12, getdate())
END
DECLARE #Pre6WorkingDay date = CASE
WHEN datepart(dw, getdate()) IN (2) THEN dateadd(day,-9, getdate())
WHEN datepart(dw, getdate()) IN (1) THEN dateadd(day,-8, getdate())
ELSE dateadd(day,-7, getdate())
END
select p.GTIN, p.FirstScanned as FirstScan, p.Created As lastScan
from
(
select p.GTIN
,p.LocationID
,p.Created
,min(p.Created) over (partition by p.GTIN) as FirstScanned
,max(p.Created) over (partition by p.GTIN) as LastScanned
from Products123 p
) p
where p.LastScanned = p.Created and LocationID not in (15,16,17) AND p.FirstScanned < #Prev8workingdays
Order by FirstScanned
My result looks like this:
GTIN | FirstScanned | LastScanned
12345678910 | 2017-06-30 14:58:07.693 |2017-08-01 11:36:16.460
But it Should be:
GTIN | FirstScanned | LastScanned
12345678910 | 2017-08-01 11:34:16.347 |2017-08-01 11:36:16.460

Answer 1

You can get there just using a simple case statement. Take the max date for location 1, and that will be the latest date
select p.GTIN, p.FirstScanned as FirstScan, p.Created As lastScan
from
(
select p.GTIN
,p.LocationID
,p.Created
,max(case when p.LocationID=1 then p.Created else null end) over (partition by p.GTIN) as FirstScanned
,max(p.Created) over (partition by p.GTIN) as LastScanned
from Products123 p
) p
where p.LastScanned = p.Created and LocationID not in (15,16,17) AND p.FirstScanned < #Prev8workingdays