如何使用计算字段声明这个SQL表?

create table Son
(
    ID int primary key identity(1,1),
    DateOfBirth datetime,
    constraint Age check (datediff(year,DateOfBirth,GetDate())>= 0),
    Name nvarchar(50) not null check (len(Name) >= 8) default('Sergio')
)
create table Son
(
    ID int primary key ident