Re: [Zsqlml-users] some questions about coding zsqml selects

[Matthew L. <lei...@ma...>]

Dear Adrian,

Thanks for your reply.  Let me explain where I'm coming from, too.  There 
are lots of plug-and-play database-driven web applications.  Take two, 
like phpslash and bugzilla.  Each of them have their separate databases 
with some kind of user/password table.  What if you wanted them to use the 
SAME user and password information?  One way is to go in and rewrite all 
the queries, but that's going to take a while.  What if you can write 
functions that will break up the query and rewrite them intelligently 
based on specified rules?  So if bugzilla wants "user_id" of the 
table "users" in the database "bugs", and we want to instead query 
"author_id" of the table "psl_authors" in the database "phpslash", then we 
could write a rule for that.

I'm not a professional programmer, but it seems like a possible way to do
this is to use regexps to break up the SQL into some kind of XML, use XSLT
to apply your integration rules, convert it back to SQL and only then give
it to the database server.  I guess there are some performance issues with 
that, but it seems to me to be feasible and not too hard to apply.  You 
wouldn't have to change much code, just write the stylesheet.

So I looked for an XML method to write SQL statements and the one included
in zsqlml was the first one that looked well thought out.  It did seem 
more designed for database creation and population than for querying, but 
I was hoping that that could be extended, and I'm glad you think so.  One 
thing that I wonder about is that so many attributes are of type ID...so 
you can't have a column of a table of a database with all the same name, 
right?  

MySQL allows you to reference columns by dbname.tablename.colname, and you 
can select and even compare across multiple databases.  I don't know if 
this is supported in other RDBMSs, or if it conforms to any SQL standard.

I don't know much java at all...my background is PHP, Perl, and a tiny bit
of C.  But I'll take a look at the stylesheets you've written and see if
it can be ported to mysql.  You're probably right that it shouldn't be
hard.

Take care.

--Matthew Leingang


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Matthew Leingang                http://www.math.rutgers.edu/
Rutgers University              lei...@ma...
Department of Mathematics       "This signature needs no quote."