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

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")
    )]
)