On 30/11/2010 5:10pm, Victor Hooi wrote:
Mike,
Hmm, I'm currently using a recursive ('self') Many2Many and ForeignKey
for Children and Spouse, respectively (see source in the first post).
Is that what you meant?
Or perhaps I'm not quite getting what you mean - any chance you could
paste a models.py example so I can make sure I'm on the same page?
Victor
I'm keeping track of companies, divisions and people with their
relationships. For example, divisions can be traded between companies
and people consult to companies or own trading entities. I can also keep
track of pretty much any relationship of interest.
Hope this helps ...
class Entity(models.Model):
"""
Entities can be corporations or humans. entity_type indicates
which.
"""
entity_type = models.CharField(max_length=MEDIUM, blank=False,
choices=ENTITY_TYPES,
default=ENTITY_TYPES[0][0])
entity_name = models.CharField(max_length=LARGE, blank=False)
entity_title = models.CharField(max_length=SMALL, blank=True)
other_name = models.CharField(max_length=LARGE, blank=True)
slug = models.SlugField(max_length=VLARGE)
updated_by = models.ForeignKey(User, blank=True, null=True)
updated_date = models.DateTimeField(blank=True)
address = models.ForeignKey(Address, blank=True, null=True)
created = models.DateTimeField(auto_now_add=True)
saved = models.DateTimeField(auto_now=True)
saved_by = models.ForeignKey(User, blank=True, null=True,
related_name='entity_saved_by')
class Meta:
verbose_name_plural = 'entities'
def __unicode__(self):
ename = u' '.join(self.entity_title,
self.other_name,
self.entity_name)
return u'%s: %s (%s)' % (self.pk,
ename.strip(),
self.entity_type)
class Relationship(models.Model):
entity = models.ForeignKey(Entity, null=False,
related_name='rel_entity')
xref = models.ForeignKey(Entity, null=False,
related_name='xref_entity')
relationship = models.CharField(max_length=MEDIUM, blank=False,
choices=RELATIONSHIPS,
default=RELATIONSHIPS[0][0])
comment = models.CharField(max_length=HUGE, blank=True)
start_date = models.DateTimeField(blank=True, null=True)
end_date = models.DateTimeField(blank=True, null=True)
created = models.DateTimeField(auto_now_add=True)
saved = models.DateTimeField(auto_now=True)
saved_by = models.ForeignKey(User, blank=True, null=True,
related_name='relationship_saved_by')
def __unicode__(self):
return u'%s: %s ' % (self.relationship, self.xref)
Mike
Cheers,
Victor
On Nov 30, 5:02 pm, Mike Dewhirst<mi...@dewhirst.com.au> wrote:
On 30/11/2010 4:26pm, Victor Hooi wrote:
heya,
Phone Number - Yup, you're both right, I'll be using CharField now,
and model validation to make sure they're digits.
Spouse/Children:
Victor
I'm coming in late on this and don't have the context for your design
but I think there might be a better (perhaps more flexible) way to
handle spouses and children without worrying about NULLs.
I really like a single table for everyone. After all spouses and
children are persons too. You can use a separate table to hold named
many-to-many relationships between the person table and itself.
If the relationship is "Spouse" then that relationship speaks for
itself. Children can simultaneously have relationships with "Father",
"Mother", "Step-mother" etc. Other persons can have "Ex-spouse"
relationships when divorced etc.
If you can find any person then you can navigate through all the
relationships to find all connected persons.
Finally, if someone has multiple spouses then they probably need
counselling but at least you can represent it with multiple relationship
records :)
Mike
With children, a M2M field, there's a link table, and if you don't
have a spouse, then there won't be any lines in that table. So no need
for NULLs there. I've just tested it with just blank=True, and no
null=True - seems to do what I want (optional children).
With ForeignKeyField though, I thought this was simply an FK field,
with the ID number of the object we're relating/pointing stored in
that field? Isn't that how it works in a normal DB? Why is there a
separate Person_spouse table?
Is there any way to make this optional without using NULLs, or should
I make it a m2m field? (I suppose in theory you can have multiple
spouses...well, not under my jurisdiction, I guess...lol).
Cheers,
Victor
On Nov 30, 3:11 pm, Lachlan Musicman<data...@gmail.com> wrote:
On Tue, Nov 30, 2010 at 12:28, Victor Hooi<victorh...@gmail.com> wrote:
Hi,
I'm wondering what the community's stance on using NULL in Django is?
Say for example you have:
class Person(models.Model):
street_address = models.CharField(max_length=50, blank=True)
suburb = models.CharField(max_length=30)
postcode = models.IntegerField()
state = models.CharField(max_length=3)
email = models.EmailField()
mobile_phone_number = models.IntegerField(max_length=12)
home_phone_number = models.IntegerField(max_length=10,
null=True, blank=True)
work_phone_number = models.IntegerField(max_length=8,
null=True, blank=True)
spouse = models.ForeignKey('self', null=True, blank=True)
children = models.ManyToManyField('self', null=True,
blank=True)
For string fields like street_address, I can make these "blank=True",
and Django will store an empty string if the user leaves it blank.
However, for integer fields like home_phone_number and
work_phone_number, I've had to make these "null=True" for the case
where somebody doesn't supply them (i.e. they're meant to be optional,
mobile is required).
However, is there a better way of handling this case? (assuming I want
to keep these fields as integers).
Is it possible to know why you would want to keep them as integers?
Given that there are no mathematical functions that you would want to
apply to them....
What about in the case of optional foreign keys (spouse and children)
- is there a better way of handling these, without using NULLs?
As I understand it, foreign keys are kept in the db as follows:
1. table_Person
2. table_Person_children
3. table_Person_spouse
table 2 has three columns: id, Person, Children
table 3 has three columns: id, Person, Spouse
or something to that effect.
Therefore, if there is no Spouse or Child, there is no entry for
Person in tables 2 or 3.
Cheers,
Victor
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