SQL Server 2019

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create table #Pressfeature
 (
  PartId int,
  PressName varchar(300),
  TechId int
);

insert into #Pressfeature
   (PartId,PressName,TechId)
values
   (1211,'AC',1),
   (2421,'grail',2),
   (6211,'compress',3);
3 rows affected

SELECT * FROM #Pressfeature;


PartId
PressName
TechId


1211
AC
1

2421
grail
2

6211
compress
3


insert into #Pressfeature(PartId,PressName,TechId) 
select  s.PartId,s.PressName,
        TechId  =  COALESCE(pf.TechId, dense_rank() over (order by s.PressName) + (select max(TechId) from #Pressfeature))
from    
(
        values
        (3900,'grail',NULL),
        (8321,'Angit',NULL)
) s (PartId,PressName,TechId)
LEFT JOIN #Pressfeature pf ON pf.PressName = s.PressName;
2 rows affected

SELECT * FROM #Pressfeature;


PartId
PressName
TechId


1211
AC
1

2421
grail
2

6211
compress
3

8321
Angit
4

3900
grail
2