[MSSQL Ex] Sincronismo tra due tabelle da 8 milioni di records

--********************
use tempdb
go
create table UNO (campo1 datetime, campo2 smallint)
go
create table DUE (campo3 datetime, campo4 smallint, campo5 datetime, delta smallint)
go
insert into UNO (campo1,campo2) values ('7-07-19 01:08:03.902',1)
insert into UNO (campo1,campo2) values ('7-07-19 01:08:05.903',0)
insert into UNO (campo1,campo2) values ('7-07-19 01:08:07.905',0)
insert into UNO (campo1,campo2) values ('7-07-19 01:08:09.912',1)
insert into UNO (campo1,campo2) values ('7-07-19 01:08:11.915',0)
insert into UNO (campo1,campo2) values ('7-07-19 01:08:16.915',0)
insert into UNO (campo1,campo2) values ('7-07-19 01:08:22.915',1)
insert into UNO (campo1,campo2) values ('7-07-19 01:08:24.915',1)
insert into UNO (campo1,campo2) values ('7-07-19 01:08:33.915',0)
insert into UNO (campo1,campo2) values ('7-07-19 01:09:18.915',1)
insert into UNO (campo1,campo2) values ('7-07-19 01:12:22.900',0)
insert into UNO (campo1,campo2) values ('7-07-19 01:14:25.903',1)
insert into UNO (campo1,campo2) values ('7-07-19 01:16:01.915',1)
go
insert into DUE (campo3) values ('7-07-19 01:08:11.902')
insert into DUE (campo3) values ('7-07-19 01:08:04.903')
insert into DUE (campo3) values ('7-07-19 01:08:07.903')
insert into DUE (campo3) values ('7-07-19 01:08:32.963')
insert into DUE (campo3) values ('7-07-19 01:08:10.903')
insert into DUE (campo3) values ('7-07-19 01:08:14.903')
insert into DUE (campo3) values ('7-07-19 01:08:28.903')
insert into DUE (campo3) values ('7-07-19 01:08:32.903')
insert into DUE (campo3) values ('7-07-19 01:08:48.903')
insert into DUE (campo3) values ('7-07-19 01:09:14.915')
insert into DUE (campo3) values ('7-07-19 01:12:25.900')
insert into DUE (campo3) values ('7-07-19 01:14:26.903')
insert into DUE (campo3) values ('7-07-19 01:16:00.915')
go
select * from UNO order by Campo1
go
-- dichiaro variabili intervallo di tempo sulla JIMP
DECLARE @down AS datetime
SET @down = '7-07-19 01:08:07.912'
DECLARE @up AS datetime
SET @up = '7-07-19 01:09:25.912'

update DUE
     set Campo4=v.Campo2, Campo5=v.Campo1
from DUE t1
cross apply (
     select top 1 Campo1,Campo2 from UNO t2
     where abs(datediff(second, t2.Campo1, t1.Campo3)) <2 and t2.Campo1>=@down and t2.Campo1<@up
     order by abs(datediff(second, t2.Campo1, t1.Campo3))
) v
go
update DUE set delta=abs(datediff(second,campo5,campo3))
go
select * from DUE order by DUE.Campo3
go
drop table UNO
go
drop table DUE
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