RE: [GENERAL][SQL] 'denormalising' with a select - Mailing list pgsql-general

Here is a version using aggregation:

    create function get_codes_agf(text, text) returns text as '
    begin
        if (length($1) > 0) then
            return $1 || '', '' || $2
        else
            return $2;
        end if;
    end' language 'plpsql';

    CREATE AGGREGATE get_codes_ag (
        sfunc1 = get_codes_agf,
        basetype = text,
        stype1 = text,
        initcond1 = ''
        );


select brecard_id, get_codes_ag(code) from table_name group by brecard_id;



> > -----Original Message-----
> > From:    Stuart Rison [SMTP:stuart@ludwig.ucl.ac.uk]
> > Sent:    Tuesday, June 01, 1999 6:54 AM
> > To:    pgsql-general@postgreSQL.org
> > Subject:    [GENERAL][SQL] 'denormalising' with a select
> >
> > Hi there,
> >
> > This was posted to SQL where it 'truly' belongs but I got no answwer and
> > since it has a bit of database design in it (and a lot more people seem
> to
> > read [GENERAL]) I thought I'd try it here.
> >
> > Consider a table like this:
> >
> > brecard_id      |code
> > ----------------+----
> > IEGA18051999006 |COME
> > IPHA04031999004 |CRIB
> > IPHA04031999005 |COME
> > IPHA04031999005 |CRIB
> > IPHA26021999006 |SOLI
> > IPHA26021999010 |COME
> > IPHA26021999010 |SOLI
> > ISTL04031999001 |CRIB
> > IUCH03031999003 |COME
> > IUCH03031999003 |CRIB
> > IUCH03031999003 |MICR
> > IUCH03031999003 |SOLI
> >
> > each combination of id and code is unique (they form a composite primary
> > key)
> > but any brecard_id could have 1 or more codes associated with it
> > (theoretically with no upper boundary but let us say a maximum of 5
> > codes).
> >
> > Is there a SELECT which will turn each of the codes for one brecard_id
> > into
> > a column... ie.
> >
> > brecard_id      |code1|code2|code3|code4|code5
> > ----------------+-----+-----+-----+-----+-----
> > IEGA18051999006 |COME |     |     |     |
> > IPHA04031999004 |CRIB |     |     |     |
> > IPHA04031999005 |COME |CRIB |     |     |
> > IPHA26021999006 |SOLI |     |     |     |
> > IPHA26021999010 |COME |SOLI |     |     |
> > ISTL04031999001 |CRIB |     |     |     |
> > IUCH03031999003 |COME |CRIB |MICR |     |
> > IUCH03031999003 |SOLI |     |     |     |
> >
> > and here a a few more brainteasers for you gurus out there...
> >
> > 1) I'm actually not fussed about the order the codes appear in the
> > columns,
> > but let's say the order mattered, would this affect the SELECT(s)?
> > 2) Would it make the query easier if I knew the maximum number of codes
> > one
> > brecard_id could have?
> > 3) (this one for true Wizards -and Sorceresses, Herouth ;)- only) Could
> > you
> > write a 'generalised' query which could cope with tables having variable
> > 'maximum' numbers of codes associated with each brecard_id?
> >
> > For the life of me I don't know how you'd do it in SQL, I have PL/pgSQL
> > and
> > have started playing around with that but I'd hate to re-invent the
> wheel!
> >
> > regards,
> >
> > Stuart.
> >
> > +-------------------------+--------------------------------------+
> > | Stuart Rison            | Ludwig Institute for Cancer Research |
> > +-------------------------+ 91 Riding House Street               |
> > | Tel. (0171) 878 4041    | London, W1P 8BT, UNITED KINGDOM.     |
> > | Fax. (0171) 878 4040    | stuart@ludwig.ucl.ac.uk              |
> > +-------------------------+--------------------------------------+