Re: Removing Functionally Dependent GROUP BY Columns
| От | David Rowley |
|---|---|
| Тема | Re: Removing Functionally Dependent GROUP BY Columns |
| Дата | |
| Msg-id | CAKJS1f9K99+dKKs2WXzXA1BQf7X=OxVsrt7BACTohTn-E3yrHQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Removing Functionally Dependent GROUP BY Columns (Peter Eisentraut <peter_e@gmx.net>) |
| Список | pgsql-hackers |
On 3 December 2015 at 14:28, Peter Eisentraut <peter_e@gmx.net> wrote:
On 11/30/15 11:00 PM, David Rowley wrote:
> It seems that there's no shortage of relational databases in existence
> today which don't support this. These databases would require the GROUP
> BY clause to include the p.description column too.
Well, actually, we implemented this because other databases had it and
users kept complaining to us.
Most likely you mean MySQL? I believe there was a bit of an influx in people emigrating away from that database not in the too distant past. It's not too surprising we picked up some of those people, and some of the features that they were used to at the same time... IF NOT EXISTS perhaps is a good example to back that up.
However, I think your comment makes it quite clear that we're not talking about the same database management systems.
For me, I tested the most popular 2 commercial ones and found neither of these supported columns in the SELECT list which were functionally dependent on the GROUP BY clause, unless the columns themselves were in the GROUP BY clause. I admit my "no shortage" comment was based on these two only. I also admit that I don't possess any statistics which show which RDBMSs users are migrating from. I merely thought that testing the two most popular commercial ones was enough justification to write what I wrote.
--
David Rowley http://www.2ndQuadrant.com/
David Rowley http://www.2ndQuadrant.com/
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