This will take all rows from 1st table and only 1st row from second table
select * from myTable
union all (select top 1 * from myTableDuplicate)
Output
Id fName
1 Srikanth
2 sunil
3 Shilpa
1 Srikanth
This will take all the columns from the first table and only Id column from the second table
select * from myTable M
join (select ID from myTableDuplicate) as D on M.Id=D.ID
Output
Id fName ID
1 Srikanth 1
2 sunil 2
3 Shilpa 3