I think a select query is possible.
check this if it works for you
select
ROW_NUMBER() over(partition by Glno, Name order by Glno, Name) Slno, Glno, Name
from cc
Try this
select
ROW_NUMBER() over(partition by Glno, Name order by Glno, Name) Slno, Glno, Name
into ccTemp from cc
go
drop table cc
go
sp_rename 'ccTemp','cc'
go
select Slno, Glno, Name from CC