Julian Einwag - rockenstein AG <jein...@rockenstein.de> writes:
> So basically the following in ANSI syntax would be equivalent:
> select web_customer.id, web_contact.id
> from web_customer left join web_contact on web_customer.id = web_contact.id
> and 1 = web_contact.id
I've never been perfectly clear about how Oracle's syntax works either :-)
So if you were to leave off the (+) on that WHERE condition,
it would be equivalent to putting the condition into WHERE instead of
JOIN/ON in ANSI syntax, correct?
Also, at least in Postgres, the result of doing the latter would be that
you didn't get an outer join at all: the optimizer would conclude that
no null-extended row could get past the WHERE clause, so it would reduce
the left join to a plain join. I assume Oracle's optimizer knows that
too. So you need to (+)-mark *every* clause involving variables from
the inner side of the intended left join, or it won't work as desired.
Seems like a bit of a foot-gun ...
regards, tom lane
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