Hi

I don't know if this is a good place to ask but I take my chances.

I have small project on my hands. I have two databases. One containing
data about people and their interests and the other one with where to
find information that could interest those people.

Now I need to write some kind of program probably in C++ or something
like that to cross-reference those two databases and send, let say,
emails to people that could be interested in that information.

It's the first time I'm doing the project like that so I'm
looking for any references to this kind of database programming or
anything that could help me.

Thank you very much.
Ralph

rzajac (AT) gmail (DOT) com wrote:
I don't have any specific solution for you, but I would suggest it
would be easier if all the information was in one database. Then you
could use the power of SQL to make the connections. Otherwise you are
going to replicate a lot of the query functionality in your application
program.

Ed.

Ed Prochak wrote:
For what it's worth, some RDBMS implementations (e.g. MySQL) can do
cross-database queries in SQL. Though many RDBMS implementations do not
support this.

The syntax is simply to use databasename.tablename where you would use
tablename. For example:

SELECT a.*, b.*
FROM database1.table_a AS a
JOIN database2.table_b AS b ON a.col1 = b.col2

This is supported only if the two databases reside on the same server.

Regards,
Bill K.

So it is possible to cross reference data from two databases just using
SQL queries?

Do you know where can I find some examples of this kind of query and
database designs? (books, Internet, ...)

Once again I'll say that my goal will be to find potentially
interesting information for people based on many levels of comparison.
The closest analogy would be dating sites sending emails about
potential matches based on profiles with selected requirements.

Thank you for your help.
Ralph

rzajac (AT) gmail (DOT) com wrote:
Like I said, it depends on the RDBMS software implementation you are
using. Are you using MySQL? That's the only one I know supports
cross-database joins, but there may be others. You need to make sure
(that is, read the documentation) that the RDBMS you use supports this
feature.

By the way, are you clear on the distinction between a "database" and a
"table"?

As for the specific queries to use, that depends on the database design
you have, and the types of comparisons you want to make. I can't guess
anything about your database from what you have told us.

Regards,
Bill K.

On 13 May 2006 14:10:49 -0700, rzajac (AT) gmail (DOT) com wrote:

So far the responses have been taking the two databases statement
at face value, but I see a possible vocabulary problem.

A database is a collection of data organised for quick access.
(There is more to it, but this suffices for this discussion.) A
database may have more than table of data.

Do you really have two databases, or do you have two tables?

If the former, read what the other posters have said. If it is
two tables, then you need to learn about joins.

Do not presuppose the language. The query might be done quite
easily by the DBMS (database management system).

Sincerely,

Gene Wirchenko

Bill Karwin wrote:
DB2 does support this via federation/nicknames. I assume Oracle and
SQLServer implements something similar, but I dont know


/Lennart

[...]

I have two separate databases. I never did something like that before
so I'm just asking where should I go from here - what books would you
suggest or maybe some online tutorials.

Thank you very much for help so far.

Ralph

rzajac (AT) gmail (DOT) com wrote:
MySQL docs:
http://dev.mysql.com/doc/refman/5.0/...ualifiers.html

I'm assuming you are using MySQL. I asked you that question but you
didn't answer it.

Regards,
Bill K.