MySQL: Set user variable from result of query

Is it possible to set an user variable based on the result of a query in MySQL?

What I want to achieve is something like this (we can assume that both USER and GROUP are unique):

set @user = 123456;
set @group = select GROUP from USER where User = @user;
select * from USER where GROUP = @group;

Please note that I know it’s possible but I do not wish to do this with nested queries.