How do I filter by time in a date time field?

Question

In the model \'entered\' is a datetime field. I want to query the data to find all entry\'s that where made between noon(start_time) and 5:00pm (end_time).

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Answer 1

You can use range to filter in between. I found this the best way to filter since SQL does filtering better than Django.

fromRange=datetime.datetime.strptime(request.GET.get('from'),'%Y-%m-%dT%H:%M:%S.%fZ')
toRange=datetime.datetime.strptime(request.GET.get('to'),'%Y-%m-%dT%H:%M:%S.%fZ')

entry = Entry.objects.filter(entryTime__range=(fromRange,toRange))

Answer 2

I suggest filter x<=arg and exclude x>=arg2.

Answer 3

I don't believe there's built-in support for this, but you can pass extra where-clause parameters (warning: some possibility of introducing DB-dependent behaviour here).

For example, on Postgres, something like:

Entry.objects.extra(where=['EXTRACT(hour from entered) >= 12 and '\
                    'EXTRACT(hour from entered) < 17'])

If you're using potentially unsafe input to determine the values 12 and 17, note that you can also specify a params option to extra that will ensure proper quoting and escaping, and then use the standard sql %s placeholders in your where statement.

Answer 4

Using SQLite as an example, a relatively clean and generic solution would be:

Entry.objects.extra(where=["time(entered) between '%s' and '%s'"],
                    params=[start_time.strftime("%H:%M"), end_time.strftime("%H:%M")])

Answer 5

I just figured out a solution for a similar use case – perhaps someone finds this useful:

In my case, I have Availability and Constraint models like so (simplified):

class Availability(...):
    start = models.DateTimeField()
    end = models.DateTimeField()

class Constraint(...):
    from = models.TimeField()
    to = models.TimeField()

I wanted to find availabilities that don't violate any constraints.

With Postgres, this worked for me:

Availability.objects.extra(
    where=['NOT (start::time, "end"::time) OVERLAPS (\'{0}\'::time, \'{1}\'::time)'.format(
        from.strftime("%H:%M"), to.strftime("%H:%M")
    )]
)

Note how you can cast DateTime to Time (or rather timestamp to time without timezone in Postgres terms) with ::time and then use OVERLAPS to compare the time ranges.

And in regards to the original question, you can also do:

Availability.objects.extra(
    where=['start::time BETWEEN \'{0}\'::time AND \'{1}\'::time AND
            "end"::time BETWEEN \'{0}\'::time AND \'{1}\'::time'.format(
        from.strftime("%H:%M"), to.strftime("%H:%M")
    )]
)

Answer 6

You could filter in python instead using the db's mechanisms:

for e in Entry.objects.all():
   if i.entered.hour>= 9 and i.entered.hour < 17 :# or break down to minutes/seconds
        list.append(e)

but both solutions are ugly, i think.

Steve, you have to decide, what is less ugly for you:

• processsing a lot of data in a for-loop,
• or use .extra(..) and by-passing the orm-system