How to update the colomn based on the other colmn data

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Hi Team,

I have a data table contains the below information.

Name Guid
Junnu e10e4d76-3a59-4ad0-9476-76a2d5d47e17
Punnu New guid
Dunnu New guid
Junnu e10e4d76-3a59-4ad0-9476-76a2d5d47e17

Here is the explanation:If the first colmn (Name) Repeated the guid should be same
and if not repeated(unique).It Should has new guid.How to achieve this