SQL Server query same values First value from the result show in first row | Only first row from a specific Column with same value

Example : If you want to show the result like that , If you use master detail table like Loan & loan payment return partially against same lone then you want to show details Loan amount & partially received amount then this is usefull for you.

ID	Flag	Amount
1	A	200
2	A	200
3	A	200
4	B	100
5	B	100
6	C	300
7	C	300
8	C	300

But I like to display like this:

ID	Flag	amount
1	A	200
2		0
3		0
4	B	100
5		0
6	C	300
7		300

Solution ::

You can use lag window function,

select t.ID, 
    case when lag([Flag]) over(order by ID)=[Flag] then '' else [Flag] end [Results]
from t

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