[Tfug] More RDBMS stuff

[Bexley Hall]

Hi,

Hopefully a *simple* question re: PostgreSQL
(or, any other "enterprise class" RDBMS?).

I understand the concept/purpose behind
TABLESPACEs.  It adds a capability to the
DBMS that you can't really *get* in any
other way!

But, I am having a hard time trying to 
understand the need for "DATABASEs" and,
in particular, "SCHEMAs".  Nearest I can
tell, they are just "convenience notions"
that don't *really* add any new capability
you can't get using other mechanisms (?).

It *appears* that they just allow you to 
partition the namespace.  Is there some
other benefit to using / NOT using them?

Since I tend to like thinking hierarchically,
my first inclination is to group components
of particular "applications" into DATABASEs.
I.e., an HVAC database for environmental
control stuff, an IRRIGATION database for
stuff related to watering the yard, an
ADDRESS database for "contact list" stuff,
etc.

And, have no real "need" for the concept of
SCHEMAs (at least based on *my* understanding
thereof).

However, PostgreSQL appears to lock you into
a single database -- as a "sandbox", of sorts.
So, references to tables in *other* databases
are prohibited!  :<  Of course, this is NOT
what I want.

Epiphany!  Schemas give me the partitioning
that I desire without the "electric fence"
between these partitions (that the database
approach enforces).

Is *this* the sole point of schemas?  To 
allow the namespace to be artificially
subdivided while retaining access to objects
in other schemas in the same database?

(Uh, d'uh?)

Aside from the added *naming* complexity that
this necessitates (yeah, I know about schema 
search orders), are there any other downside 
issues, here that I'm not smart enough to see?

Can anyone point to a good *modern* text
covering these issues?  I have some of
Date's classic writings but I think they
predate many of these concepts :<  The
single PostgreSQL text that I have is so
laughable that the man(1) pages are more
worthwhile.  :<  And, MySQL seems to lag
PostgreSQL significantly so I doubt they
address these issues/features, yet.  :<
My Oracle texts are written as "references"
so only *remind* folks of things they 
already *know*!  <frown>

Thanks!
--don


       
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