QuerySet.extra: group by weekday on a date field

[László Károlyi]

Hey,

I'm coming from the ​Django doc, where you say that I should try to avoid using QuerySet.extra in the future, and report the thing I want to achieve here, so you could improve the ORM. Here's the thing:

I have a mysql table where there is a date field. I'd like to do a DAYOFWEEK(date) calculation on it, then GROUP BY its result, and then do some MIN/MAX/AVG calculation on another field in the table. The point is to get the minimum/maximum/average values for the days of the week.

Currently this does not seem possible with even using the extra parameter.

Or is it?

Tips welcomed, but I actually have given up on creating this query out of the ORM.

[Simon Charette]

Hi Karolyi,

As you can't build the query using QuerySet.extra() in the first time I'm going to close this ticket as invalid. You should be able to annotate your queryset using Func(F('datefield'), function='DAYOFWEEK') (or ExtractWeekDay on Django 1.10+) and use values() before your min/max/avg annotate() call to group by your annotated day of week.

Please see ​the section about values() in the aggregation docs for more details and our support channels.

[László Károlyi]

Thx @charettes,

I got helped on #django-dev, the same information was told. Using Func solved my problem, however it's mysql specific, so I don't consider it a future proof solution.

I'll change it when 1.10 is out. Until then, I can use it this way.