John Kaufmann wrote:
In a message dated 2008.06.19 22:00 -0500, Drew Jensen wrote:
Keith Clark wrote:
Is it possible to link two databases through one table? I want to share
a products table between two different databases, as an example.
Short answer is NO - you can not at this time do that.
Drew, sorry to go back more than a year in the archive in my search
for this answer, but...
If it is not possible to link two databases through one table, does
that mean that every application must be organized as a single
database? That seems like an awkward limitation - yet I have not found
a way around it.
[Example application: our church. Databases are at least three:
Persons; Property; Events. Persons must link to Property (as in: who
is responsible for doing what, and how do we get in touch with them?)
or Events (ditto); likewise, Property must link to Events. For
example, of many tables within Persons database, at least two
("Person", "Group") must link to other databases. Trying to put all
of these elements within a single database seems impossibly unwieldy -
so how is the application practically partitioned?] Setting aside
that I expose my newbiness with such questions, I'm sure that I have
overlooked something, because these must be standard organizational
questions. Can you point me to a reference on how these connections
are resolved?
John
Hi John
well, I suppose that is why the mailing list is archived, so folks can
go back and look.
Anyway - multiple databases.
Ah - this really shouldn't be a 2 minute answer and I don't mind taking
the time to answer it, but that time is kind of limited this evening - I
will make the time over the next day or two.
Short answer for the moment:
Your database can include multiple tables, each table represents one
entity. (person, property, event)
The data in the tables can be related to each other.
Some databases (Relation Database Management Systms [RDBMS] such as
MySQL, PostgreSQl, SQL Server, Oracle) can refer to tables held within
other databases, others do not.
A database is part of an ODF defined datasource.
The datasource can CONNECT to exactly one database.
A datasource might be a reference to a full blown RDBMS or it could be
to a flat file (*.txt, *.csv, *.ods) or to a collection of files (*.dbf).
A datasource can also contain external settings for the particular
database objects (tables), such as persistent filters for tables or
pre-defined query definitions.
An OpenDocument Database Frontend Document (a Base file) is a container.
The information for "connecting to" a particular datasource is stored in
the file.
Table filters and query definitions are also stored in the Base file.
Data entry form definitions are contained within the file.
Report definitions are contained within the file.
In one particular case, embedded HSQLdb, the actual data is also
contained in the file.
HSQLdb does not support linking to external databases, but is a full
RDBMS, so your person, property and event entities would be separate
tables within the database.
HSQLdb does support linking to TEXT files that are stored externally
from the database.
Anyway - I hope that helps and doesn't just make it less clear. I will
try to put something a bit more coherent together on this later.
Drew
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