J is correct.

As for SQL, the old one will work too for this particular case:

declare @I int

select @I = (select count(convert(varchar(2),ID)+Keyvalue) from #new

group by (convert(varchar(2),ID)+Keyvalue)

having count(convert(varchar(2),ID)+Keyvalue) >1)

set @I = @I-1

set rowcount @I

delete #New where convert(varchar(2),ID)+Keyvalue

in

(select convert(varchar(2),ID)+Keyvalue from #new

group by (convert(varchar(2),ID)+Keyvalue)

having count(convert(varchar(2),ID)+Keyvalue) >1)