Select unique random rows from the SQL Server table but still duplicates

i am not the best with sql but i try my best to get my Problems done. I have a table "just" which is filled with Columns ( ID (PK, Identity), Char, Serv , Random ) . Now i want to select a random row from this table and insert it into the Table "f_WinGet". So far all my Procedures take this Step fine , but i always get Duplicates in the second table.

First table : 84 rows Second table: needed 35 random out of 84.

I have tried many other ways but i always get the same result. All my Procedure for random are binded to a Button i a C# Programm. All is working fine so far , but i always have some Duplicates of Rows in my Table.

INSERT INTO f_TWinGet SELECT TOP 1 Percent Char, Serv, Random FROM ( select distinct Char, Serv, Random from dbo.just) as derived1 ORDER BY CHECKSUM(NEWID())

It would be nice , if anyone hase an Idea how i can fix my Problem. I am still trying , but all what i get are always the same result.

With a table as small as yours you can use something like:

INSERT INTO f_TWinGet SELECT TOP 1 j.Char, j.Serv, j.Random FROM dbo.just j LEFT JOIN f_TWinGet f ON f.Char = j.Char AND j.Serv = f.Serv AND j.Random = f.Random WHERE f.Char IS NULL ORDER BY NEWID()

This way making sure that the values you're trying to insert is not on the final table.