mysql if - how to apply to equal records

Question

Hello! staff I am trying to select and apply a rule only in equal records. I need all records to be listed, but in those that are equal, a specific rule is applied;

For example, select all client records, and in all that have the same codDeference, group and show only q has the non-blank;

I’m trying like this:

select * from clientes group by codDeReferencia where id in(select distinct codDeReferencia from clientes where dataAlteracao!='')