NOT HAVING clause?

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От Alban Hertroys
Тема NOT HAVING clause?
Дата
Msg-id 43D608DC.6020406@magproductions.nl
обсуждение исходный текст
Ответы Re: NOT HAVING clause?  (Michael Glaesemann <grzm@myrealbox.com>)
Re: NOT HAVING clause?  (Pandurangan R S <pandurangan.r.s@gmail.com>)
Re: NOT HAVING clause?  (Stephan Szabo <sszabo@megazone.bigpanda.com>)
Список pgsql-general
This is sort of a feature request, I suppose. I solved my problem, but
"NOT HAVING" seems to match better with the desired result or the way
you phrase the question in your mind, if that makes any sense...

I was hoping to write a query rather short by using a "NOT HAVING"
clause. The documentation didn't specify that, and trying it resulted in
a syntax error indeed...

My data consists of a series of images related to an object. There
should be at least one image per object with sort_order = 1. I want to
find all objects that don't match this criterium.

I have these tables (clipped a bit):
CREATE TABLE image (
    image_id    SERIAL    PRIMARY KEY,
    object_id    INTEGER NOT NULL REFERENCES object MATCH FULL,
    sort_order    SMALLINT NOT NULL DEFAULT 1
);

CREATE TABLE object (
    object_id    SERIAL PRIMARY KEY,
    name        TEXT NOT NULL
);

This is what I want, but isn't a valid query:

SELECT object_id
   FROM image
  GROUP BY object_id
  NOT HAVING sort_order = 1;

It is wonderfully short, one of the reasons I like this.

I could write this as:

SELECT object_id
   FROM object
  WHERE NOT EXISTS (
    SELECT object_id
      FROM image
     WHERE sort_order = 1
       AND object_id = object.object_id
   );

Though this does give the right results, I would have liked to be able
to use NOT HAVING. Or is there a way using HAVING that would give the
same results? I'm quite sure HAVING sort_order <> 1 doesn't mean the
same thing.

What is the general opinion on this from the developers? Did I just have
one of those wild and ridiculous ideas? :P

Regards,

--
Alban Hertroys
alban@magproductions.nl

magproductions b.v.

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