How do I Compare columns of records from the same table?

Question

Here is my testing table data:

Testing

ID      Name            Payment_Date   Fee                Amt
1       BankA           2016-04-01     100                20000
2       BankB           2016-04-02     200                10000
3       BankA           2016-04-03     100                20000
4       BankB           2016-04-04     300                20000

I am trying to compare fields Name, Fee and Amt of each data records to see whether there are the same values or not. If they got the same value, I'd like to mark something like 'Y' to those record. Here is the expected result

ID      Name            Payment_Date   Fee                Amt      SameDataExistYN
1       BankA           2016-04-01     100                20000    Y
2       BankB           2016-04-02     200                10000    N
3       BankA           2016-04-03     100                20000    Y
4       BankB           2016-04-04     300                20000    N

I have tried these two methods below. but I am looking for any other solutions so I can pick out the best one for my work.

Method 1.

select t.*, iif((select count(*) from testing where name=t.name and fee=t.fee and amt=t.amt)=1,'N','Y') as SameDataExistYN from testing t

Method 2.

select t.*, case when ((b.Name = t.Name)
                        and (b.Fee = t.Fee) and (b.Amt = t.Amt)) then 'Y' else 'N' end as SameDataExistYN
from testing t
left join ( select Name,  Fee, Amt
            from testing
            Group By Name,  Fee, Amt
            Having count(*)>1  ) as b on b.Name = t.Name
                                      and b.Fee = t.Fee
                                      and b.Amt = t.Amt

Answer 1

Here is another method, but I think you have to run tests on your data to find out which is best:

SELECT
  t.*,
  CASE WHEN EXISTS(
    SELECT * FROM testing WHERE id <> t.id AND Name = t.Name AND Fee = t.Fee AND Amt = t.Amt
  ) THEN 'Y' ELSE 'N' END SameDataExistYN
FROM
  testing t 
;