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RE: database primary keys in XML Schema

• To: <michael.h.kay@n...>
• Subject: RE: database primary keys in XML Schema
• From: "Markus Seibold" <Markus.Seibold@g...>
• Date: Fri, 13 Feb 2004 14:45:15 +0100 (MET)
• Cc: xml-dev@l...
• References: <000b01c3f22b$a88bde00$6401a8c0@pcukmka>

My XML Schema contains country, state and city elements (which correspond to
the Country, State, and City tables in the DB). 

When I want to insert a country, a state, and some cities altogether for the
first time using a XML document, the keys are not the problem because the
parser will shred the XML elements into the corresponding tables and the RDBMS
will automatically create the keys.

But what if I want to add some cities at a later point?
My idea was to design my schema in a way that it allows the city element to
be declared as document root. Doing so, I can insert only cities (using the
same XML Schema as for inserting all three parts together). 
But how can I tell the parser/RDBMS which country/state the cities to be
inserted belong to?
One idea I had was to add a attribute to the city element in order to
specifiy the RDBMS primary key for country. But the XML document creater must know
the RDBMS key in advance then ...

Thanks, Markus

> Your XML schema describes constraints on a single document. A single
> document probably corresponds to a "business object" held in your
> database. The XML Schema cannot describe constraints that apply across
> documents. Perhaps this is where your difficulty lies.
> 
> Michael Kay
> 
> > -----Original Message-----
> > From: Markus Seibold [mailto:Markus.Seibold@g...] 
> > Sent: 12 February 2004 19:29
> > To: xml-dev@l...
> > Subject:  database primary keys in XML Schema
> > 
> > 
> > Hello everybody,
> > 
> > I am developing a XML Schema which should function as an 
> > interface to a relational database. I have problems with how 
> > to design the primary keys in XML Schema.
> > 
> > 1.) When I insert data via XML instance documents the first 
> > time, I cannot specify a primary key in my XML instance 
> > document because the database automatically creates an 
> > auto-increment key. Correct?
> > 
> > 2.) What if I, for example, want to insert a city in a 
> > geography database (the database has a Country and a City 
> > table; 1:n relationship). When inserting a city, how can I 
> > specify to which country the city belongs? I needed to know 
> > the database primary key for the country, wouldn't I and add 
> > this key as an attribute to the city in my instance document? 
> > What other solutions do exist?
> > 
> > This issue cost me alot of time so far and I would really 
> > appreciate any help!
> > 
> > Thanks a lot, Markus
> > 
> > 
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-- 
Markus Seibold
------------------------------
Krebsgasse 6
D-93047 Regensburg
Germany
------------------------------
Email: markus.seibold@g...
Phone: +49 (941) 504 1009
Mobile: +49 (171) 212 6869
FAX: +49 (89) 1488 210457

• Follow-Ups:
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    • From: "Tor Helland" <tor@h...>

• References:
  • RE: database primary keys in XML Schema
    • From: "Michael Kay" <michael.h.kay@n...>

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