[gnome-db] Re: question: in memory table representation: please help

[Neil Zanella <nzanella gmail com>]

Sorry, the link I meant to refer to is:

http://www.gnome-db.org/docs/libgda/libgda-GdaTable.html

How do I create an in memory object for the SQL table described below...
(i.e. a copy of the table itself, not the data it contains).

Thanks,

Neil

On Tue, 26 Oct 2004 21:18:19 -0600, Neil Zanella <nzanella gmail com> wrote:
> Hello,
> 
> With regards to the following link:
> 
> http://www.gnome-db.org/docs/libgda/libgda-gda-util.html
> 
> I need to create an in memory representation of an SQL table,
> which happens to be just what GdaTable claims to do. That is,
> I want to model the table itself in memory, and not the data it
> contains. So, how would I model the following?
> 
> CREATE TABLE X (
>   a       VARCHAR(16),
>   b       VARCHAR(64) NOT NULL,
>   c       INTEGER NOT NULL,
>   d       VARCHAR(64) NOT NULL,
>   e       VARCHAR(8096),
>   PRIMARY KEY (a,b),
>   UNIQUE(c,d),
>   UNIQUE(d,e),
>   FOREIGN KEY (b, c) REFERENCES Y
>     ON UPDATE CASCADE ON DELETE CASCADE,
>   FOREIGN KEY (catDesc) REFERENCES Z
>     ON UPDATE CASCADE
>   CHECK (a != d)
> );
> 
> The API is missing some comments and I am really trying to guess:
> 
> So I could do:
> 
> GdaTable *x =  gda_table_new("X");
> 
> Then I find methods gda_table_new_from_model() and
> gda_table_add_field(). I assume the first method is for generic models,
> not just SQL models, so I skip it and move on to gda_table_add_field():
> since my tables are flat relational tables which are not object oriented, I
> most likely don't need a model, I guess. So then:
> 
> void        gda_table_add_field             (GdaTable *table,
>                                              const GdaFieldAttributes *fa);
> 
> So I must define 5 fields a, b, c,d, e, and set attributes for them?
> Fair enough...
> assuming each field has it's own GdaFieldAttributes (i.e. no two fields in two
> different tables will share GdaFieldAttributes, not even if they referene each
> other), I proceed and try:
> 
> GdaFieldAttributes *a = gda_field_attributes_new();
> gda_field_attributes_set_defined_size(a, 15);
> gda_field_attributes_set_gdatype(a, GDA_VALUE_TYPE_STRING);
> 
> GdaFieldAttributes *b = gda_field_attributes_new();
> gda_field_attributes_set_defined_size(b, 64);
> gda_field_attributes_set_gdatype(b, GDA_VALUE_TYPE_STRING);
> gda_field_attributes_set_allow_null(a, FALSE);
> 
> GdaFieldAttributes *c = gda_field_attributes_new();
> gda_field_attributes_set_gdatype(c, GDA_VALUE_TYPE_INTEGER);
> gda_field_attributes_set_allow_null(a, FALSE);
> 
> GdaFieldAttributes *d = gda_field_attributes_new();
> gda_field_attributes_set_defined_size(d, 64);
> gda_field_attributes_set_gdatype(d, GDA_VALUE_TYPE_STRING);
> gda_field_attributes_set_allow_null(a, FALSE);
> 
> GdaFieldAttributes *e = gda_field_attributes_new();
> gda_field_attributes_set_defined_size(e, 8096);
> gda_field_attributes_set_gdatype(e, GDA_VALUE_TYPE_STRING);
> gda_field_attributes_set_allow_null(a, FALSE);
> 
> ...
> 
> gda_table_add_field(x, a);
> gda_table_add_field(x, b);
> gda_table_add_field(x, c);
> gda_table_add_field(x, d);
> gda_table_add_field(x, e);
> 
> But now what I don't understand is how to set unique keys. Cause I have
> two of them? For primary keys, it seems like I can just:
> 
> gda_field_attributes_set_primary_key(x, a);
> gda_field_attributes_set_primary_key(x, b);
> 
> so (a, b) is the primary key.
> 
> But I have two unique keys, so how could I possibly do it?
> Same goes for foreign keys, there is more then one, so how
> does the API support creating this in memory representation
> of an SQL table if not this way?
> 
> And what about the "ON UPDATE DELETE/CASCADE" and CHECK
> constraint? The former could be coded manually. The second, I guess
> could also be checked manually. But how do I define two unique keys?
> 
> Thanks,
> 
> Neil
>