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From "Greg Monroe" <Greg.Mon...@DukeCE.com>
Subject RE: Fwd: Columnmap only support one foreingkey
Date Tue, 19 Feb 2008 22:07:13 GMT


Thomas Fischer said:
> 
> On Tue, 19 Feb 2008, Fran Ferri wrote:
> >
> > Why the columnmap only supports one related column?
> > Is an update pending?
> 
> It seems that this particular information in ColumnMap does not
support
> multiple foreign key relations per column. But as this information is
> not
> used anyway, this has not been much of a problem in the past. There
are
> currently no plans to change this behaviour.
> 

I'm not even sure why this is needed?  AFAIK, the SQL standards
specifies:

The foreign key identifies a column or a set of columns in one
(referencing) 
table that refers to a column or set of columns in another (referenced)
table. 
The columns in the referencing table must be the primary key or other 
candidate key in the referenced table. The values in one row of the 
referencing columns must occur in a single row in the referenced table.

I'd interpret this as each column can only have one matching column in a

single remote table.  If you want the "ordering" for the remote tables' 
primary key set, you can get that by looking at the remote table's 
information.

But I could be wrong about in this.  I'd be curious to see the SQL that
would define the multiple foreign key on one column.  And then to see 
how many of the common Database servers support it.
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