[DB-SIG] Strange resultset with ORDER BY col1, GROUP BY col2

Kolbe Kegel kolbe at kolbekegel.com
Fri Jun 24 17:28:11 CEST 2005

Hi Andy,

> As group_concat is a MySQL specific function I suspect that the 
> problem you are seeing is specific to the MySQLdb module.

This seems reasonable. I suppose that I ought to make an attempt to 
contact the maintainer directly. I'll look into doing so soon.

> I'm running MySQL 4.0.17 and your query doesn't work as GROUP_CONCAT 
> is not available in this version.

Upgrade! You're missing out on a lot of great features in 4.1 :)

> A couple of questions do spring to mind though;
> - Do you really need to group by one thing and order by another?

Absolutely. In my application, I want a lit of actions grouped by the 
type of action and upon whom it was performed and ordered by the most 
recently performed action in each of those groups.

> - Do you need to do the group_concat transposition in SQL or would it 
> be better achieved in Python after you've select all of the group, 
> comment pairs from the database?

Of course there are workarounds. Unfortunately, as Chris pointed out, 
the workarounds will result in unnecessary inefficiency. At any rate, 
this is almost certainly a bug in MySQLdb, so fixing that is preferable 
to developing workarounds. At this point, my workaround is to simply 
use .tostring() in my application, but that's a rather ugly and short 
term solution.

Thanks for your comments.


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