[英]Django queryset of related objects
Having the following model:具有以下模型:
class Company(models.Model):
name = models.CharField(max_length=10)
class Department(models.Model):
name = models.CharField(max_length=10)
company = models.ForeignKeyField(to=Company)
persons = models.ManyToManyField(to=Person, on_delete=models.PROTECT)
class Person(models.Model):
name = models.CharField(max_length=10)
I would like to get a queryset
of all persons in a company我想获得一个queryset
所有的人在公司
Using使用
def persons_by_company(company_name):
l = []
for d in Department.objects.filter(company__name=company_name):
for p in d.persons:
l.append(p)
return l
would be将是
What would be the way to get a queryset here?在这里获取查询集的方法是什么?
In my case, I think it's quite simple with just就我而言,我认为这很简单,只需
Person.objects.filter(departement__company__id=company_id).distinct()
or with the company name:或使用公司名称:
Person.objects.filter(departement__company__name__iexact=company_name).distinct()
Your function would become:你的功能会变成:
def persons_by_company(company_name):
return Person.objects.filter(departement__company__name__iexact=company_name).distinct()
It returns a queryset and it's faster.它返回一个QuerySet,它的速度更快。 I use iexact
to avoid case sensitive.我使用iexact
来避免区分大小写。
UPDATED: .distinct()
Just to remove duplicate entries.更新: .distinct()
只是为了删除重复的条目。
First you must have foreign key binded to your company or department首先你必须有外键绑定到你的公司或部门
class Department(models.Model):
name = models.CharField(max_length=10)
company = models.ForeignKeyField(to=Company, related_name="department_company_key")
class Person(models.Model):
name = models.CharField(max_length=10)
person_department = models.ForeignKey(
'Department',
related_name="person_department_key"
on_delete=models.CASCADE,
blank=False,
null=False
)
then in your function:然后在你的函数中:
def persons_by_company(company_name):
l = []
for d in Department.objects.filter(company__name=company_name):
for p in d.person_department_key.all(): # You also apply some filter()
l.append(p) # Remember This will append object not string or dictionary
return l
Don't forget that related name must be unique不要忘记相关名称必须是唯一的
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