How to query all entries from past 6 hours ( datetime) in GQL?

问题

I have a simple table in Google App Engine with a date field. I want to query all the rows with the date field valued between now and 6 hours ago. How do I form this query?

回答1:

SELECT * FROM simpletable
WHERE datefield < DATETIME(year, month, day, hour, minute, second)

computing those year, month, &c, in your application code.

回答2:

I know you say GQL, but here's a python helper function I use:

import datetime
def seconds_ago(time_s):
    return datetime.datetime.now() - datetime.timedelta(seconds=time_s)

There may well be a more concise way to write it: I'm not a python expert and went with the first thing that worked. Take a look at the datetime docs if you care. It's used like this:

my_query = MyTable.all().filter("date >", seconds_ago(6*60*60))

I'm sure that can be translated to GQL without much bother, but I prefer the object-oriented interface, and I don't know the necessary DATETIME syntax.

In python the query is then used like this:

# get a count
my_query.count()
# get up to 1000 records
my_query.fetch(1000)
# iterate over up to 1000 records
for result in my_query:
    # do something with result

来源：https://stackoverflow.com/questions/994187/how-to-query-all-entries-from-past-6-hours-datetime-in-gql