How about this:

select * from #tReceive;

with basedata as (

select

rn = row_number() over (partition by JobNumberID, PONUMBER, DELIVNOTE, [DATE] order by ORDERKEY)

, JobNumberID

, PONUMBER

, DELIVNOTE

, DATE

, ORDERKEY

, TYPE

, Quantity

from

#tReceive

), rCTE as (

select

NEWID() PoReceiveHeaderGuid

, JobNumberID

, PONUMBER

, DELIVNOTE

, DATE

, ORDERKEY

, TYPE

, Quantity

, rn

from

basedata

where

rn = 1

union all

select

r.PoReceiveHeaderGuid

, bd.JobNumberID

, bd.PONUMBER

, bd.DELIVNOTE

, bd.DATE

, bd.ORDERKEY

, bd.TYPE

, bd.Quantity

, bd.rn

from

rCTE r

inner join basedata bd

on (r.JobNumberID = bd.JobNumberID and

r.PONUMBER = bd.PONUMBER and

r.DELIVNOTE = bd.DELIVNOTE and

r.[DATE] = bd.[DATE])

where

r.rn = case bd.rn when 1 then 0 else 1 end

)

--select

-- r.PoReceiveHeaderGuid

-- , r.JobNumberID

-- , r.PONUMBER

-- , r.DELIVNOTE

-- , r.DATE

-- , r.ORDERKEY

-- , r.TYPE

-- , r.Quantity

--from rCTE r

--order by

-- r.JobNumberID

-- , r.PONUMBER

-- , r.DELIVNOTE

-- , r.DATE

-- , r.ORDERKEY

update tr set

PoReceiveHeaderGuid = r.PoReceiveHeaderGuid

from

#tReceive tr

inner join rCTE r

on (tr.JobNumberID = r.JobNumberID and

tr.PONUMBER = r.PONUMBER and

tr.DELIVNOTE = r.DELIVNOTE and

tr.[DATE] = r.[DATE]);

select * from #tReceive;