sql - Cannot create Foreign Key Constraint -


i have simple address book collects people , companies info. have following 3 tables , others email, phonenumber, address linked contact:

create table [dbo].[contact] (     [id]        int           identity (1, 1) not null,     ...     constraint [pk_contatto] primary key clustered ([id] asc) );  create table [dbo].[person] (     [id]            int           identity (1, 1) not null,     [idcontact]    int           not null,     [idcompany]     int           null,     ...     constraint [pk_person] primary key clustered ([id] asc),     constraint [fk_person_company] foreign key ([idcompany]) references [dbo].[company] ([id]) on delete set null on update cascade,     constraint [fk_person_contact] foreign key ([idcontact]) references [dbo].[contact] ([id]) on delete cascade on update cascade );  create table [dbo].[company] (     [id]          int          identity (1, 1) not null,     [idcontact]  int          not null,     ...     constraint [pk_company] primary key clustered ([id] asc),     constraint [fk_company_contact] foreign key ([idcontact]) references [dbo].[contact] ([id]) on delete cascade on update cascade );

basically want if deletes contact person/company associated deleted. also, if deletes company associated person, idcompany of person must set null.

the constraint cannot created due "loop creation or additional propagation path creation" fk_person_contact.

what missing?

i suspect 'loop creation' because person table references contact table , company table , company table references contact table.

can person record , company record reference different contact records?

person -> contact -> company -> contact b

or should person record , company record reference same contact?

person -> contact -> company -> contact a

how relationship between contact, person , company defined?

  • 1 contact has many persons?
  • 1 contact has many companies?
  • 1 person has many contacts?
  • 1 person has 1 company?
  • 1 person has many companies?
  • 1 company has many contacts?
  • 1 company has many persons?

it may need think 1 or more link tables model relationship properly.


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