Primary Keys

[Rui Monteiro]

Mello,

 

I was wondering why canto r how can I put 2 primary keys on a table?

 

Here's na example on Oracle language:

 

CREATE TABLE FacturaMusica(

            CodFactura number(4), CONSTRAINTS FK_FacturaMusica_CodFactura
FOREIGN KEY(CodFactura) REFERENCES Factura(CodFactura),

            CodMusica number(4), CONSTRAINTS FK_FacturaMusica_CodMusica
FOREIGN KEY(CodMusica) REFERENCES Musica(CodMusica),

            CONSTRAINT PK_FacturaMusica PRIMARY KEY(CodFactura,CodMusica)

);

 

This is very usefull to break "n" to "n" relations.

 

Any tip?

 

Thanks

 

Rui