Re: [gnome-db] GdaSqlBuilder and WHERE clauses

[Vivien Malerba <vmalerba gmail com>]

On 4 May 2010 16:45, Murray Cumming <murrayc murrayc com> wrote:
> On Tue, 2010-04-27 at 21:41 +0200, Vivien Malerba wrote:
>> On 27 April 2010 18:03, Murray Cumming <murrayc murrayc com> wrote:
>> > In Glom, I have several generic functions that combine a fixed SQL query
>> > with various WHERE clauses. Imagine something like this
>> >
>> >  DataModel get_data_from_table(string where_clause)
>> >
>> > It does this by doing a simple string concatenation.
>> >
>> > But how can I do this with SqlBuilder, whose gda_sql_builder_add_cond()
>> > expects the details of the condition in terms of arguments and
>> > operator?:
>> > http://library.gnome.org/devel/libgda/unstable/GdaSqlBuilder.html#gda-sql-builder-add-cond
>> >
>> > Ideally, I think I'd have a GdaSqlBuilderCond object that I could pass
>> > around and even AND with another GdaSqlBuilderCond.
>>
>> So if I understand you'd like to have a function as:
>> DataModel get_data_from_table(GdaSqlBuilderCond where_clause)
>>
>> I would prefer to avoid creating a new object just for this case, and
>> prefer to add more flexibility to the GdaSqlBuilder by allowing the
>> import/export of parts of a statement (as an opaque GdaSqlAnyPart
>> pointer):
>>
>> GdaSqlAnyPart *gda_sql_builder_export_part (GdaSqlBuilder *b, guint id);
>
> How would I know what id to parse?

It's the ID returned by gda_sql_builder_add_cond() in the
GdaSqlBuilder refered to in step 1/6 below.

>
>> and
>> guint gda_sql_builder_import_part (GdaSqlBuilder *b, guint id,
>> GdaSqlAnyPart *part);
>>
>> With these 2 new calls you can create a
>> DataModel get_data_from_table(GdaSqlAnyPart where_clause):
>>
>> 1- create a GdaSqlBuilder with the where clause you want
>
> A complete SQL query, part of which I would then ignore after exporting
> the WHERE clause?

As only the WHERE part will be used, you don't even need the
GdaSqlBuilder in step 1 to contain a valid SQL statement (it may only
contain a WHERE clause if you prefer, it does not matter).

>
>> 2- export that WHERE clause as a GdaSqlAnyPart, and use it as argument
>> to your get_data_from_table() function
>> 3- create a new GdaSqlBuilder with the specific SQL you need
>> 4- import the GdaSqlAnyPart into that builder object
>> 5- get the GdaStatement and execute it.
>> 6- discard the unneeded objects
>>
>> How does it sound?
>
> I'd be happy to try that out, please.

Ok, I'll make the proposed API changes along with an example usage.

Vivien