create table dbo.General (id int primary key, parent_id int null, name varchar(50));
create table dbo.Company (id int primary key, name varchar(50));
create table dbo.SparePart (id int primary key, name varchar(50), company_id int);
create table dbo.Model (id int primary key, name varchar(50), sparePart_id int);

insert into dbo.Company values (1, 'Apple'), (2, 'Siemens'), (3, 'Nokia');
insert into dbo.SparePart values (1, 'display', 2), (2, 'battery', 2), (3, 'display', 1), (4, 'microphone', 3);
insert into dbo.Model values (1, 'aaaa', 1), (2, 'bbbb', 2), (3, 'cccc', 2), (4, 'dddd', 3);
go

declare @t table (id int identity primary key, name varchar(50), table_id int, table_key int, table_parent_key int);

insert into @t
 (name, table_id, table_key, table_parent_key)
 select name, 1, id, null from dbo.Company;

insert into @t
 (name, table_id, table_key, table_parent_key)
 select name, 2, id, company_id from dbo.SparePart;

insert into @t
 (name, table_id, table_key, table_parent_key)
 select name, 3, id, sparePart_id from dbo.Model;

insert into dbo.General
 (id, parent_id, name)
 select
  a.id, b.id, a.name
 from
  @t a left join
  @t b on b.table_id = a.table_id - 1 and b.table_key = a.table_parent_key;

select * from dbo.General;
go

drop table dbo.General, dbo.Company, dbo.SparePart, dbo.Model;
go