Re: Fwd: Re: Referencing

lucas(at)presserv(dot)org wrote:
> Ok,
> But the problem is becouse the "buy" and "send" tables referencing with other
> father table, wich is different.
> I shoud not create a spent table to put the "buy" and "send" values
> becouse the
> entire database is more complex than it. look:
>
> create table output(
> id serial primary key,
> client integer references clientes,
> fiscal_number varchar(30),
> print_date date,
> ...
> );
> create table SEND(
> id serial primary key,
> output integer references input,
> product_id integer,--references....
> value money
> );
> create table input(
> id serial primary key,
> supplier integer references suppliers,
> employee varchar(30),
> ...
> );
> create table BUY(
> id serial primary key,
> input integer references input,
> product_id integer,--references....
> value money
> );
>
> ---and---
>
> create table financial(
> id serial primary key,
> cred_deb smallint,
> value money,
> references integer references ???, --<<-HERE IS THE PROBLEM, it will
> reference
> to buy OR send table
> );
>
> How looked, the "buy" and the "send" table is identical except the father
> references (INPUT or OUTPUT)... Then I shoud not create ONE table (spent) wich
> has these informations.
> And now my question: Is there a way to references (financial) with two
> diferents
> tables in the some row? Or need I create two diferents rows???
>
> Thanks. (sorry for my english).
>

It's hard to say without knowing more precisely what you are trying to
model, but I think this push you in the right direction:

-- This table takes the place of both SEND and BUY
create table activity(
id serial primary key,
product_id integer, --references....
value money
);

create table financial(
id serial primary key,
cred_deb smallint,
value money,
activity_id integer references activity
);

create table output(
id serial primary key,
client integer, --references clientes,
fiscal_number varchar(30),
print_date date,
activity_id integer references activity
);

create table input(
id serial primary key,
supplier integer, -- references suppliers,
employee varchar(30),
activity_id integer references activity
);

And then you do the following:

create view buy
as
select
a.id,
b.id as "input_id",
a.product_id,
a.value
from
activity a
join input b on b.activity_id = a.id;

The SELL view is left as an exercise for the reader.

--
Daryl Richter
Platform Author & Director of Technology

(( Brandywine Asset Management )
( "Expanding the Science of Global Investing" )
( http://www.brandywine.com ))