Group Rows by Date - tsql

Question

I have been asked to group transactions that have occurred within two minutes of one another into separate "date groups". I'm having a tough time wrapping my head around how to split the data by minutes.
I wrote a test table below along with expected "date groups"
CREATE TABLE #tmpData
(ID int,actionDt datetime)
INSERT INTO #tmpData
(ID,actionDt)
VALUES
(1, '7/22/2021 9:51'),
(1, '7/22/2021 9:52'),
(1, '7/22/2021 9:55'),
(1, '7/22/2021 9:56'),
(1, '7/22/2021 9:57'),
(1, '7/22/2021 9:58'),
(1, '7/22/2021 10:00'),
(1, '7/22/2021 10:10'),
(2, '7/22/2021 8:38'),
(2, '7/22/2021 8:39'),
(2, '7/22/2021 8:40'),
(2, '7/22/2021 12:05')
the expected "date groups" should be
id
DtGroup
1
7/22/2021 9:51
1
7/22/2021 9:55
1
7/22/2021 9:58
1
7/22/2021 10:10
2
7/22/2021 8:38
2
7/22/2021 12:05
I wrote the below which gets close but the timestamps 9:58 and 10:00 for ID 1 should be their own date group.
;with resultSet AS
(
SELECT a.id, a.actiondt, a.diff FROM
(
SELECT
id,
actiondt,
diff = datediff(mi,lag(actiondt) OVER (PARTITION BY id ORDER BY actiondt),actiondt)
FROM #tmpdata
) AS a
WHERE diff IS NULL OR diff > 2
)
SELECT
t.id,
t.actiondt AS currDt,
resultset.actiondt AS DtGrp
from #tmpdata t
left JOIN resultset
on t.id = resultset.id
and t.actiondt between dateadd(mi,-2,resultset.actiondt) and dateadd(mi,2,resultset.actiondt)

Answer 1

Is the logic 2 minutes or greater between actionDt? If so should the expected results be the following? Otherwise, I don't understand your expected results to try to help.
(1, '7/22/2021 9:51'),
(1, '7/22/2021 9:55'),
(1, '7/22/2021 9:57'),
(1, '7/22/2021 10:00'),
(1, '7/22/2021 10:10'),
(2, '7/22/2021 8:38'),
(2, '7/22/2021 8:40'),
(2, '7/22/2021 12:05')
This will give you the above results.
declare #Count int, 
#LoopCount int,
#PrevMinutes int,
#CurrentMinutes int,
#NextMinutes int,
#PrevFlag int,
#Flag int
;with dID as (
select distinct id,
actiondt
from #tmpData
)
select
identity(int,1,1) RowNo,
d.id as Grp,
d.actiondt,
lag(DATEPART(mi, d.actiondt), 1,0) over (order by d.actiondt) as PrevMinutes,
DATEPART(mi, d.actiondt) as CurrentMinutes,
lead(DATEPART(mi, d.actiondt), 1,0) over (order by d.actiondt) as NextMinutes,
0 as flag
into #Temp
from #tmpData d
full outer join dID on d.id = dID.id
and d.actiondt = dID.actiondt
order by d.id, actiondt
select #Count = ##RowCount 
set #LoopCount = 1 
while #LoopCount <= #Count 
begin 
set #PrevMinutes = (select PrevMinutes from #Temp where RowNo = #LoopCount)
set #CurrentMinutes = (select CurrentMinutes from #Temp where RowNo = #LoopCount)
set #NextMinutes = (select NextMinutes from #Temp where RowNo = #LoopCount)
set #Flag = (select flag from #Temp where RowNo = #LoopCount)
set #PrevFlag = (select flag from #Temp where RowNo = #LoopCount - 1)
if (#LoopCount = 1)
begin
update #Temp
set flag = 1
where RowNo = 1
end
else if (abs(#PrevMinutes - #CurrentMinutes) >= 2)
begin
update #Temp
set flag = 1
where RowNo = #LoopCount
end
else if (#PrevFlag = 0 and #Flag = 0)
begin
update #Temp
set flag = 1
where RowNo = #LoopCount
end
    set #LoopCount=#LoopCount + 1 
end 
select Grp as id,
actiondt
from #Temp
where flag = 1