2008/10/1 Fulvio Senore <mailing@...>:

> Daniel Albuschat ha scritto:
>
>> There's an important thing to know
>> here: I'm fetching
>> only the primary keys from a result set to know how many rows there
>> are and which
>> primary key the row at the temporary "index" in my table has.
> This is very interesting, since I thought that it would have been a
> difficult task.
> If your rows come from a join a single primary key is not enough: to
> identify a row you need the primary key of all the table used in the join.
> So it looks like your software needs to parse the SQL statement and to
> automatically identify all the needed primary keys. At a second time,
> when you need to retrieve the full row, you need to recreate if from the
> primary keys.

Well, I made my life easy here. You provide two distinct statements,
one to select the primary key(s) and one to select the data.
The library then sets as many parameters as primary keys have been
selected to the data-statement and executes it. It's quite easy to use
and was easy to implement, because parsing SQL is nothing you
should really try to do.

> I am not a Firebird expert, and I have written my own data access layer
> on top of IBPP to satisfy my needs. It works well enough, but when I
> create an editable rowset from a single table I pass the name of the
> primary key as a parameter because I had no idea of hot to determine it
> automatically.
> It is not a big problem, but it would be nice to have the software
> determine the primary key. Do know hot it can be done?

select
s.rdb$field_name
from
rdb$relations r
left join
rdb$relation_constraints c
on
c.rdb$relation_name=r.rdb$relation_name and
c.rdb$constraint_type='PRIMARY KEY'
left join
rdb$index_segments s
on
s.rdb$index_name=c.rdb$index_name
where
r.rdb$relation_name=YOUR TABLE NAME
order by
s.rdb$field_position


Regards,

Daniel Albuschat

--
eat(this); // delicious suicide