可以使用分析函数执行此操作：

select t.*,
       coalesce(manager,
                first_value(manager ignore nulls) over (order by sales desc)
               ) as imputed_manager
from t;

如果您真的想在更新中使用它，那么：

update t
    set manager = (select max(manager) keep (dense_rank first order by sales desc nulls last)
                   from t
                   where manager is not null
                  )
    where manager is null;

我不喜欢这样直接改变数据。看起来很危险。