| From: | Craig Ringer <craig(at)postnewspapers(dot)com(dot)au> |
|---|---|
| To: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
| Cc: | francois(dot)perou(at)free(dot)fr, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: SQL compatibility reminder: MySQL vs PostgreSQL |
| Date: | 2010-03-06 09:05:17 |
| Message-ID: | 4B921ACD.9090004@postnewspapers.com.au |
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| Thread: | |
| Lists: | pgsql-advocacy pgsql-hackers |
Andrew Dunstan wrote:
> But AIUI that won't be the same as the MySQL behaviour, as documented at
> <http://dev.mysql.com/doc/refman/5.5/en/group-by-hidden-columns.html>:
>
> When using this feature, all rows in each group should have the same
> values for the columns that are ommitted from the |GROUP BY| part.
> The server is free to return any value from the group, so the
> results are indeterminate unless all values are the same.
That sounds a lot like the behavior of `DISTINCT ON (...)' and it'd
actually be really rather useful to have under some circumstances.
Whether it should be written as 'GROUP BY', though, isn't so clear.
--
Craig Ringer
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