Re: Using ODBC database

From:

"William DePalo [MVP VC++]" <willd.no.spam@mvps.org>

Newsgroups:

microsoft.public.vc.language

Date:

Wed, 31 May 2006 16:01:59 -0400

Message-ID:

<e4HyU0OhGHA.1508@TK2MSFTNGP04.phx.gbl>

"Jonathan Blitz" <jb@anykey.co.il> wrote in message
news:uEaQ4hNhGHA.764@TK2MSFTNGP03.phx.gbl...

I am using a PostgreSQL database and want to connect to it using ODBC.

OK.

I have used an external ODBC connector (libodbc++) to connect. This works
perfectly for fetching data.

I'm not familiar with that class library. Just btw I don't recall having
seen it discussed here.

So - I created a database source using the wizard and use it as a basis to
get data. This works ok but I cannot see how to switch between different
datasources. I tried editing the connection string but it still goes to
the
original data source.

I also looked at the online doctumentation and it talks about the
CDatabase
class and that seems to be different again!

So, what am I supposed to be using?

Well, you can use a class library or you can use the native ODBC API. In
either case you probably should search for a more appropriate group to post
the question.

That said, I can't help with libodbc or MFC's ODBC classes but at the level
of the API this is the deal:

You allocate a "environment" handle with
        SQLAllocHandle(SQL_HANDLE_ENV, ...);

That makes your application a consumer of ODBC services. Within that
environment you can create one or more database "connections". You do that
by calling

    SQLAllocHandle(SQL_HANDLE_DBC, ...)

to get an "empty" (my word) handle to a database connection. That done you
can use any of a number of services to connect to a DBMS. Among them is
SQLDriverConnect() which can optionally display dialogs if you have an
"incomplete" (my word) connection string.

Now once you have a connection, you can pass the connection handle to

    SQLAllocHandle(SQL_HANDLE_STMT, ...)

to retrieve a statement handle. If you have multiple datasources you just
allocate multiple connection handles, on each connect to a data source and
create a statement handle. The SQL statements that you "prepare" or
"execute" on those statement handles are routed by ODBC to the proper data
source.

--
Regards,
Will

"I'm not ready to make nice, I'm not ready to back down ..."