Question

Here’s what I have so far:

create table rubro (
  id_rubro int primary key,
  nombre_rubro nvarchar(150)
)
go

create table cliente (
  id_cliente int primary key,
  direccion nvarchar(400),
  telefono int,
  nit int
)

Answer 1

You just need to create the missing two tables and link them to the cliente table:

create table natural (
  id_cliente int primary key,
  nombre nvarchar(50),
  app nvarchar(50),
  apm nvarchar(50),
  ....
)

alter table dbo.natural
  add constraint fk_natural_cliente
      foreign key(id_cliente) references dbo.cliente(id_cliente)

and the same for the juridico table, too.

In SQL Server, those are just three regular tables, linked by foreign key constraints. Using an OR mapper such as Entity Framework gives you the ability to map those as descendant classes in your .NET domain model – but on the database level, those are just three regular tables – nothing “magic” about them…