Thread: RE: [INTERFACES] How to implement referential facilities in Postg reSQL

Check the contrib/spi/refint.* in the distribution.  To answer your
question you use triggers to implement it.  In Postgres v6.4 and higher
you could also use rules to implement referential integrity (for
examples see src/test/regress/sql/rules.sql).

    -DEJ

> -----Original Message-----
>     Hi everybody,
>
>      Happy New Year to you all.
>
>
>    We have a rather large M$ Access application for time and
> attendance
> and job time registration. It has been implemented in M$
> Access using a
> M$ Access database running on a M$ 'operating system'.
>
>    One of our issues is to use the PostgreSQL in stead
> of/underneath the
> M$ Access database application, which is the existing
> application running
> well on M$ Access with not so large amounts of data. We of course need
> to run this on a Linux box. The application makes extensive
> use of some
> Access 'referential features'.
>
>    So my question is:
>
>    What is the equivalent of
>
>      'Enforce Referential Integrity',
>      'Cascade Update Related Fields', and
>      'Cascade Update Related Records' in
>
> SQL/PostgreSQL terms. In other words, how do I get these
> facilities into
> my PostgreSQL database? I need to be able to have the M$
> Access application
> to link directly to the PostgreSQL tables using ODBC, which I
> have managed
> to copy directly using Access, but with no Primary/Foreign
> keys what so ever.
>
>
>    Thanks for any sugestions,
>
>   Leif
>
>

(see attached file)

I have two tables HEADER and DETAIL linked by an external key

I need to have the following integrity:

1. Don't allow to insert DETAILS if doesn't exist the HEADER with the
same
   key.

2. Delete in cascade all DETAILS if one cancel the HEADER having the
same key.

3. UPDATE in cascade the key of all DETAILS if one change the HEADER
key.

-Jose'-DROP TABLE header;
CREATE TABLE header (
        distretto        CHAR(4)  NOT NULL,
    anno            DECIMAL(4)  NOT NULL,
    numero            INTEGER  NOT NULL,
    data            DATE      NOT NULL,
    azienda            CHAR(11) NOT NULL,
        CONSTRAINT k_header PRIMARY KEY (distretto,anno,numero)
    );

DROP TABLE detail;
CREATE TABLE detail (
        distretto        CHAR(4)  NOT NULL,
    anno            DECIMAL(4) NOT NULL,
    numero            INTEGER NOT NULL,
    cod_prestazione        CHAR(05) NOT NULL,
        quantita        FLOAT(4) NOT NULL,
    importo            FLOAT(8),
        CONSTRAINT k_detail PRIMARY KEY (distretto,anno,numero,cod_prestazione),
        CONSTRAINT k_extern FOREIGN KEY(distretto,anno,numero) references HEADER
    );

drop function f_not_add_detail();
create function f_not_add_detail() returns opaque as '
declare
    /* to avoid insert detail if header doesn''t exist */
    tot int;
begin
    select numero into tot from header
        where anno = new.anno and numero = new.numero;
    if not found then
        raise notice ''Impossible add new detail!'';
        return NULL;
    else
            return new;
    end if;
end;
' language 'plpgsql';

create trigger t_not_add_detail before insert
    on detail for each row execute procedure f_not_add_detail();


--EXAMPLE:
select * from header;
select * from detail;
INSERT INTO detail VALUES ('E14','1999',2,'IMPOSSIBLE',123,345.5); --impossible
INSERT INTO header VALUES ('E14','1999',2,current_date,1235);
INSERT INTO detail VALUES ('E14','1999',2,'AB',523,35.5);
INSERT INTO header VALUES ('E14','1999',1,current_date,1235);
INSERT INTO detail VALUES ('E14','1999',1,'A1',423,45.5);
INSERT INTO detail VALUES ('E14','1999',1,'AC',123,345.5);
select * from header;
select * from detail;

drop function f_upd_key_detail();
create function f_upd_key_detail() returns opaque as '
declare
    /* change in cascade the key of every detail if header key is changed */
    tot int;
begin
    update detail
          set anno = new.anno, numero = new.numero
      where anno = old.anno and numero = old.numero;
        return NULL;
end;
' language 'plpgsql';

drop trigger t_upd_key_detail on header;
create trigger t_upd_key_detail after update
    on header for each row execute procedure f_upd_key_detail();

--EXAMPLE:
select * from header;
select * from detail;
update header set anno='1997', numero=33 where numero = 1 and anno='1999';
select * from header;
select * from detail;


drop function f_del_cascade();
create function f_del_cascade() returns opaque as '
declare
    /* cancel in cascade all details after header is deleted */
begin
    delete from detail
        where anno = old.anno and numero = old.numero;
        return NULL;
end;
' language 'plpgsql';

drop trigger t_del_cascade on header;
create trigger t_del_cascade after delete
    on header for each row execute procedure f_del_cascade();


--EXAMPLE:
select * from header;
select * from detail;
delete from header where anno = 1997;
select * from header;
select * from detail;