Parent Model:
id = auto_generated
add_me = IntegerField()
Child Model:
id = ForeignKey(Parent)
my_date= DateTime(auto_now_add=True)
and,
today = django.util.timezone.now()
time = today - timedelta(days=10)
now I want to retrieve records as:
child.objects.filter(my_date__lte= time +
(timedelta(days=1)*F('id__add_me')))
Everthing works fine except:
(timedelta(days=1)*F('id__add_me'))
I am using MYSQL: I get:
django.db.utils.ProgrammingError:
(1064, "You have an error in your SQL syntax;
check the manual that corresponds to your MySQL
server version for the right syntax to use near
'* `parent`.`add_me`))))' at line 1")
Query Generated is like:
SELECT* FROM `child INNER JOIN `parent` ON
(`child`.`id` = `parent`.`id`) WHERE
( `child`.`my_date` <= ((2018-07-30 09:11:18.670900
+ (INTERVAL '86400.000000' SECOND_MICROSECOND * `parent`.`add_me`))))
As you can see * (multiplication) is with INTERVAL.
I hard coded query putting the parent.add_me inside the INTERVAL and got it right,
how can I do so via Django? i.e. DATE_ADD in django
I want to reduce days from a datetime field, where days are stored in master table field.
Maybe it doesn't work with MYSQL, so please provide an alternative solution to such.
UPDATED:
Somehow I found error by writing MYSQL query as:
SELECT * FROM child INNER JOIN parent ON" \
child.id = parent.id WHERE
child.my_date<= '" + str(time) + \
"' + INTERVAL parent.add_me DAY "
The problem was with single quotes (') i.e. in mysql for <= the datetime shall be within single quotes else won't work. i.e.
2018-07-30 09:11:18.670900 shall be written as
'2018-07-30 09:11:18.670900' if adding with INTERVAL,
But as queries are generated by Django, how do I achieve that?
