Re: [gnome-db] XML Query proposal

[Gerhard Dieringer <Gerhard Dieringer nexgo de>]

Am 2001.09.27 11:06 schrieb(en) Rodrigo Moya:
> On Thu, 2001-09-27 at 09:43, Laurent Marzullo wrote:
> > Hello,
> > 
... 
> > And the second if for the description of the Query. That follows your
> > XML Query proposal. So I want to write the query:
> > 
> >     SELECT  owner,
> >             object_name,
> >             object_type
> >     FROM    ALL_OBJECTS
> >     WHERE   object_name = :p_owner  -- p_owner is a C
> variable
> >     ORDER BY OWNER, TABLE_NAME
> > 
> > And use the following XML:
> > 
> > <?xml version="1.0"?>
> > 
> > <query op="FETCH" >
> >     <param  source="ALL_OBJECTS" >OWNER</param>
> >     <sources>
> >         <table  id="ALL_OBJECTS">ALL_OBJECTS</table>
> >     </sources>
> >     <values>
> >         <field  source="ALL_OBJECTS" name="OWNER" />
> >         <field  source="ALL_OBJECTS" name="OBJECT_NAME" />
> >         <field  source="ALL_OBJECTS" name="OBJECT_TYPE" />
> >     </values>
> >     <qualification>
> >         <equal>
> >             <field source="ALL_OBJECTS" name="OWNER" />
> >             <param name="OWNER" />
> >         </equal>
> >     </qualification>
> > </query>
> > 
> > 
> > First question is: HOW TO WRITE THE ORDER BY (following your XML
>                 
> > format)?
> > 
> > The second is: May I add some tag and attribute value ?
> >            query.op = "FETCH" 
> >            <param> (parameter of the query, as the query will be
> >                    transform to PRO*C/C++)
> > 
> > Thank you very much
> > 
> I can't answer in detail those questions since I don't know in detail
> the XML query stuff (that's Gerhard who could answer those).
> 
> Anyway, if you use the XML queries specification, you shouldn't bother
> at all about the XML format yourself, but you should use the gda_xql_*
> classes to create the GdaXqlQuery object which will build the XML for
> you.
> 
> Another thing is that XML queries are right now not understood yet by
> any providers, so before you start using this for your program, support
> should be added to providers so that they understand the XML queries.
> 

According to the last gda-xml-query.dtd in libgda-0.2.91/lib/gda-common,
the query should look like:


<?xml version="1.0"?>
<!DOCTYPE query SYSTEM "./xmlquery.dtd">

<query>
  <select>
    <targetlist>
      <target name="all_objects" id="t"/>
    </targetlist>
    <valuelist>
      <value id="v01">
        <field source="t" name="owner"/>
      </value>
      <value id="v02">
        <field source="t" name="object_name"/>
      </value>
      <value id="v03">
        <field source="t" name="object_type"/>
      </value>
    </valuelist>
    <where>
      <eq>
        <field source="t" name="p_owner"/>
        <const value="xyz" type="VARCHAR"/>
      </eq>
    </where>
    <order>
      <valueref source="v01"/>
      <valueref source="v02">
    </order>
  </select>
</query>

The value attribute of the const tag ('xyz') has to be set by your
application.

As you can easily verify, the gda-xml-query.xsl tranformation reproduces
your SQL statement:

select t.owner as v01, t.object_name as v02, t.object_type as v03 
from all_objects as t  
where (t.p_owner = xyz) order by t.owner, t.object_name


------------
Gerhard