Clarify the ordering guarantees in combining queries (or lack thereof)
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. Thanks, Shay [1] https://www.postgresql.org/message-id/[email protected] [2] https://www.postgresql.org/docs/current/queries-union.html
Re: Clarify the ordering guarantees in combining queries (or lack thereof)
On Wed, Jul 13, 2022 at 5:08 PM Shay Rojansky 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.
RE: No documentation exists about ecpg ORACLE comptaible mode
Bruce Momjian wrote: > This is a very good point. I have studied the issue and created the attached > patch to document Oracle-compatibility mode. Hi Bruce, thank you for writing the document. I checked it and I'm very glad! Regards, Takeshi Ideriha
