On Tue, Apr 9, 2019 at 12:01 PM Charles Wilt <charles.wilt@xxxxxxxxx> wrote:
I think most RDBMS type applications offer the option for a "pass through
query" when connecting to an RDBMS of a different vendor.
OK. I stand corrected.
But I am not used to the idea of connecting to a database... FROM a
database. That is, it doesn't occur to me that I would be in the
situation that I would be writing SQL *in* Db2 or Oracle or whatever,
and be connecting to some *other* database. That's just a totally
foreign architecture to me.
If I'm writing an application that needs to access databases from two
different vendors (or two databases on different machines, regardless
of vendor), then I'm working in a host language which is external to
all databases, and is a client to all databases. (For that matter,
when I'm working with ONE database, I'm working in a host language
which is external to that database. This includes SQLRPGLE.)
With that in mind, I have a somewhat different take on this:
I think most RDBMS's aren't as dumb as MS products about trying to pull
back the entire table, so the requirement for a pass through query isn't
quite as in your face.
You may be right that pulling back an entire table is a uniquely dumb
behavior only exhibited by MS products (I don't know enough to confirm
that), but I don't think that is the *main* problem. I think the main
problem is that MS embeds database functionality in unexpected places.
If you're writing in a programming language like Python or RPG, you
know that the language doesn't have anything built in that will
execute SQL. Most general-purpose languages don't even have an SQL
parser built in. So it's very clear that when you write SQL in those
host languages, the SQL is being executed (and very likely even
parsed) in the target database. In such an environment, there
*couldn't* be any query other than a pass-through query.
So, as I understand it, it would be more accurate to say that whether
a query is pass-through or not is only relevant when the client has
the capacity to process queries directly itself.
John Y.
midrange.com
