Issuing standard SQL commands from clients

[Vivien Malerba <malerba linuxbox com>]

On jeu, 10 fév 2000, Rodrigo Moya Piernavieja wrote:

> 
> Well, reading through this mail, I've remembered a problem I found when
> implementing the new XML stuff, which is: how can I issue standard SQL commands
> (such as "select * from table" or "update ....") in a way understable by all the
> providers? because there are placesin the GDA libs
> (gda_xml_table_new_from_gda_recordset and this GnomeDbReport) where you must
> issue these commands. The first thing that comes to my mind is to use standard
> SQL (SQL92 or something like that?), but, what will happen with no-DBMS providers
> (LDAP, XML, ...)? and maybe standard SQL means less flexibility for some
> providers that do have extra stuff.
> 

There might be the possibility to use a tree structure to make a request. I
think every DBMS uses an internal structure to represent a query. It is a
structure (and can be a tree of structures) which can represent any operation
the DBMs can do. Why wouldn't we use the same technique, that is the client
builds the structure he wants, and gives it to the provider which is in charge
of converting that structure to SQL statements (or whatever...).

The advantages I see in this method are:
- it can be easily extended to non DBMS providers.
- it can use all the extra stuff that some providers can have.
- it is flexible.
- it is possible to use XML to convert any of these structs to text (to save
it, or even to feed the provider so that no IDL modification is necessary).

If you think it a good idea, I can have a look at how the Postgres DBMS uses
these structures and trees.

Cheers

Vivien