Re: [GENERAL] 3 tables join update

From: rihad <rihad(at)mail.ru>
Date: Sun Sep 30 2007 - 05:01:30 EDT

Richard Broersma Jr wrote:
> --- rihad <rihad@mail.ru> wrote:

>> UPDATE Foo foo
>> SET foo.baz_id=baz.id
>> FROM Baz baz LEFT JOIN Bar bar ON (foo.bar_id=bar.id)
>> WHERE bar.id IS NULL;

>
> This query cannot work. Basiclly, you are trying to set the foo.baz_id = baz.id for records in
> foo that do not yet exist. Doing this is impossible.
>

Sorry the query failed victim of me trying to simplify it so I forgot the foo=bar join. Here's a 2 table join suffering from the same problem: I want the update only when bar.common_field IS NULL:

UPDATE Foo foo
SET ...
FROM LEFT JOIN Bar bar USING(common_field) WHERE blah='blah' AND bar.common_field IS NULL;

ERROR: syntax error at or near "JOIN"

I know I'm misusing UPDATE ... FROM because I don't really want Bar's values to go into Foo, but only using them for a conditional update (atomically I hope).

---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
       choose an index scan if your joining column's datatypes do not
       match

Received on Sun Sep 30 05:04:38 2007