LEFT JOIN vicekrat na jednu tabulku ale dle ruznych vazebnich poli

[Vladimir Naprstek]

Martin Och wrote:

> Dobry den.
>
> Marne premyslim jak napsat neco takoveho:
>
> select pole2.table1, pole2.table2, pole2.table3, pole2.table4 from table1
> left join table2 on pole5.table1=pole1.table2
> left join table3 on pole6.table1=pole1.table3
> left join table4 on pole7.table1=pole1.table4
>
> POZOR table2=table3=table4 - JEDNA TABULKA
>
> Nevim, jestli je to takhle srozumitelne.
> Hlavni tabulka table1 obsahuje vazebni pole pole5-7 na tabulku table2

Předně, syntaxe je database_name.table_name.field_name (tzn. table1.pole2
např).
Potom, používáte-li MySQL, v manuálu v kapitole 8.6.1 Find all
non-distributed twins je pěkný příklad.
(tab. twin_data, person_data se vyskytují v klauzuli where dvakrát. Vtip je
v použití aliasů -> twin_data AS td on... poprvé a twin_data AS td2 on ...
podruhé).

A nemáte-li ten manuál, tady je ten dotaz.
select
        concat(p1.id, p1.tvab) + 0 as tvid,
        concat(p1.christian_name, " ", p1.surname) as Name,
        p1.postal_code as Code,
        p1.city as City,
        pg.abrev as Area,
        if(td.participation = "Aborted", "A", " ") as A,
        p1.dead as dead1,
        l.event as event1,
        td.suspect as tsuspect1,
        id.suspect as isuspect1,
        td.severe as tsevere1,
        id.severe as isevere1,
        p2.dead as dead2,
        l2.event as event2,
        h2.nurse as nurse2,
        h2.doctor as doctor2,
        td2.suspect as tsuspect2,
        id2.suspect as isuspect2,
        td2.severe as tsevere2,
        id2.severe as isevere2,
        l.finish_date
from
        twin_project as tp
        /* For Twin 1 */
        left join twin_data as td on tp.id = td.id and tp.tvab = td.tvab
        left join informant_data as id on tp.id = id.id and tp.tvab =
id.tvab
        left join harmony as h on tp.id = h.id and tp.tvab = h.tvab
        left join lentus as l on tp.id = l.id and tp.tvab = l.tvab
        /* For Twin 2 */
        left join twin_data as td2 on p2.id = td2.id and p2.tvab = td2.tvab
        left join informant_data as id2 on p2.id = id2.id and p2.tvab =
id2.tvab
        left join harmony as h2 on p2.id = h2.id and p2.tvab = h2.tvab
        left join lentus as l2 on p2.id = l2.id and p2.tvab = l2.tvab,
        person_data as p1,
        person_data as p2,
        postal_groups as pg
where
        /* p1 gets main twin and p2 gets his/her twin. */
        /* ptvab is a field inverted from tvab */
        p1.id = tp.id and p1.tvab = tp.tvab and
        p2.id = p1.id and p2.ptvab = p1.tvab and
        /* Just the sceening survey */
        tp.survey_no = 5 and
        /* Skip if partner died before 65 but allow emigration (dead=9) */
        (p2.dead = 0 or p2.dead = 9 or
         (p2.dead = 1 and
          (p2.death_date = 0 or
           (((to_days(p2.death_date) - to_days(p2.birthday)) / 365)
            >= 65))))
        and
        (
        /* Twin is suspect */
        (td.future_contact = 'Yes' and td.suspect = 2) or
        /* Twin is suspect - Informant is Blessed */
        (td.future_contact = 'Yes' and td.suspect = 1 and id.suspect = 1) or

        /* No twin - Informant is Blessed */
        (ISNULL(td.suspect) and id.suspect = 1 and id.future_contact =
'Yes') or
        /* Twin broken off - Informant is Blessed */
        (td.participation = 'Aborted'
         and id.suspect = 1 and id.future_contact = 'Yes') or
        /* Twin broken off - No inform - Have partner */
        (td.participation = 'Aborted' and ISNULL(id.suspect) and p2.dead =
0))
        and
        l.event = 'Finished'
        /* Get at area code */
        and substring(p1.postal_code, 1, 2) = pg.code
        /* Not already distributed */
        and (h.nurse is NULL or h.nurse=00 or h.doctor=00)
        /* Has not refused or been aborted */
        and not (h.status = 'Refused' or h.status = 'Aborted'
        or h.status = 'Died' or h.status = 'Other')
order by
        tvid;

Snad Vám to bude ku prospěchu....

--
Vladimir Naprstek
e-mail vladimir.naprstek na prodeco.cz