Re: [HACKERS] JOIN syntax. Examples?

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От Thomas G. Lockhart
Тема Re: [HACKERS] JOIN syntax. Examples?
Дата
Msg-id 3675B4CD.99DC208D@alumni.caltech.edu
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Ответ на Re: [HACKERS] JOIN syntax. Examples?  ("Oliver Elphick" <olly@lfix.co.uk>)
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> > This one conflicts with Postgres' operator extensibility features, 
> > since it would look just like a legal operator.
> so does =

But in fact its usage for joins matches the typical usage elsewhere.

> Has anybody tried out DB2 ?
> I have downloaded it (for linux) but have not yet tried it.

Just downloaded it this morning (and afternoon, it's a thin pipe at home
for 60MB of files :) Have you looked at what it takes to do an
installation yet?

> Not to mention that both =* and =(+) are more concise and easier to
> follow, at least for one with my headshape.
> The standard is probably the 'worst common denominator' or something
> like that :(

DeJuan points out a major strength of the SQL92 syntax, which allows
multiple outer joins in the same query. One of my books shows an
example:
 select * from   q1 full outer join q2 on (q1.id = q2.id)      full outer join q3 on (coalesce(q1.id,q2.id)=q3.id)
fullouter join q4 on (coalesce(q1.id,q2.id,q3.id)=q4.id)
 

I suppose one can do something similar using a *= operator by using
parentheses? Not sure though...
                      - Tom


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