Re: At what ANSI/SPARC level are you, when creating new... totally lost

On 14 jul, 00:23, kaja_love..._at_yahoo.com wrote:
> hello
>
> I just started learning about databases and already I'm totally lost
>
> 1) When you use,for example, SQL statements to create tables and
> implement relationships with  primary and foreign keys, do you operate
> at level three ( internal/logical model ) of ANSI/SPARC architecture,
> or at level 2 ( conceptual model ) 

At the conceptual level.

> Thus, by creating a new database are you creating logical model or
> conceptual model?

The external model and the conceptual model are both logical models.

I've seen articles on the ANSI/SPARC architecture that insert a logical layer between the conceptual layer and the internal layer, but that is nonsense.

> 2)
> Also, if in, say relational database, model created by administrator
> ( by defining new tables and keys ) is called logical model, then at
> what ANSI/SPARC level is relational model at?

At the conceptual level and the external level, but not at the internal level because there you will describe aspects of the physical organization of the data which is not part of the relational model.

> 3)
> What is the difference between model and scheme?

These terms are in this context usually used synonymously.

• Jan Hidders