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Re: Clarify the ordering guarantees in combining queries (or lack thereof) - Mailing list pgsql-docs

From David G. Johnston
Subject Re: Clarify the ordering guarantees in combining queries (or lack thereof)
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Msg-id CAKFQuwZLpXqOs5JhtyLkEhv6Y6TAUK-aJuMOG9v1-zatgrZq5Q@mail.gmail.com
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In response to Clarify the ordering guarantees in combining queries (or lack thereof)  (Shay Rojansky <roji@roji.org>)
Responses Re: Clarify the ordering guarantees in combining queries (or lack thereof)  (Shay Rojansky <roji@roji.org>)
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On Wed, Jul 13, 2022 at 5:08 PM Shay Rojansky <roji@roji.org> wrote:
Greetings.

I was trying to understand what - if any - are the guarantees with regards to ordering for combining queries (UNION/UNION ALL/...). From this message[1], it seems that UNION ALL does preserve the ordering of the operand queries, whereas UNION does not (presumably neither do INTERSECT, INTERSECT ALL, EXCEPT and EXCEPT ALL).

The documentation[2] makes no mention of this, I'd suggest adding a note clarifying this.


Since the documentation doesn't make a guarantee there is none.  If you want ordered output use ORDER BY.

David J.

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