Re: BUG #17150: Unexpected outputs from the query
| От | David G. Johnston |
|---|---|
| Тема | Re: BUG #17150: Unexpected outputs from the query |
| Дата | |
| Msg-id | CAKFQuwaxSxw+T3dmyOoNLW=zrL5yPz3_ecaVMdVyihYCTMa9rw@mail.gmail.com обсуждение исходный текст |
| Ответ на | BUG #17150: Unexpected outputs from the query (PG Bug reporting form <noreply@postgresql.org>) |
| Ответы |
Re: BUG #17150: Unexpected outputs from the query
|
| Список | pgsql-bugs |
On Tuesday, August 17, 2021, PG Bug reporting form <noreply@postgresql.org> wrote:
This
unexpected return can be fixed by removing "ORDER BY ( SELECT COUNT ( v1 )
)", then the query returns sum="0" as expected.
Well, PostgreSQL cannot remove the order by otherwise it would be a different query. So your suggestion is spot on, and the user should probably do that, but it doesn’t seem like a bug.
As "SELECT 1" returns a single row (even though there isn't even a from clause) the fact that "select count(*)" returns a row with a count of 1 isn't surprising - it always returns at least one row. So the order by expression adds a row to the output. This may be surprising but is also a natural consequence of allowing pretty much any desired expression to appear in the order by clause.
David J.
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