Re: joining tables

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On Tue, Sep 3, 2019, 19:44 Jack Royal-Gordon <jackrg(at)pobox(dot)com> wrote:

> Let me step back a bit, as I realize upon further reflection that the
> first method will not work.
>
> As far as the issue about two “Ted” records, read it as though I said two
> “Ted D” records. It refers to two records in the same table with the same
> key value. If “Ted D” appeared twice in table 1 and twice in table 2, the
> join would give four resulting records (all combinations of the records
> from table 1 and the records from table 2 (and the records from table 3) —
> that’s fundamentally how a join works. If you don’t want that, then make
> sure that there are no duplicates within each of the tables.
>
> > On Sep 3, 2019, at 9:35 AM, TedJones <ted(at)mentra(dot)co(dot)uk> wrote:
> >
> > Hi Jack
> >
> > I'm not sure if I understand your comment about two 'Ted' fields and
> > duplication of rows. In the example below there is 'Ted' twice in Table3
> 1
> > and 3 and must appear twice as I've shown in the result as the data in
> the
> > rest of the row is different. I agree with no duplication of rows if all
> of
> > the row is the same.
> >
> > Ted
> >
> > Table: 1
> > Author Title Sales Publication Date
> > Jim A aa I
> > Ted B bb J
> > Dave C cc K
> > Ted D dd L
> >
> > Table: 2
> > Author Publisher
> > Jim him
> > Ted me
> > Dave me
> > Will you
> > Gary him
> >
> > Table:3
> > Author Title Country
> > Ted B UK
> > Ted D US
> > Jim A UK
> > Dave C UK
> >
> > Combined table: Result
> > Author Title Publication Date Publisher Sales
> Country
> > Ted B J me bb UK
> > Ted D L me dd US
> > Jim A I him aa UK
> > Dave C K me cc UK
> > Gary null null him null null
> > Will null null you null null
> >
> >
> >
> >
> > --
> > Sent from:
> https://www.postgresql-archive.org/PostgreSQL-pgadmin-support-f2191615.html
> >
> >
>
>
>
>