django_数据库操作—增、删、改、查

>>> from datetime import date
>>> book = BookInfo(
    btitle='西游记',
    bpub_date=date(1988,1,1),
    bread=10,
    bcomment=10
)
>>> book.save()
>>> hero = HeroInfo(
    hname='孙悟空',
    hgender=0,
    hbook=book
)
>>> hero.save()
>>> hero2 = HeroInfo(
    hname='猪八戒',
    hgender=0,
    hbook_id=book.id
)
>>> hero2.save()

>>> HeroInfo.objects.create(
    hname='沙悟净',
    hgender=0,
    hbook=book
)
<HeroInfo: 沙悟净>

>>> BookInfo.objects.all()
<QuerySet [<BookInfo: 射雕英雄传>, <BookInfo: 天龙八部>, <BookInfo: 笑傲江湖>, <BookInfo: 雪山飞狐>, <BookInfo: 西游记>]>
>>> book = BookInfo.objects.get(btitle='西游记')
>>> book.id
5

>>> BookInfo.objects.get(id=3)
<BookInfo: 笑傲江湖>
>>> BookInfo.objects.get(pk=3)
<BookInfo: 笑傲江湖>
>>> BookInfo.objects.get(id=100)
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/Users/delron/.virtualenv/dj/lib/python3.6/site-packages/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/Users/delron/.virtualenv/dj/lib/python3.6/site-packages/django/db/models/query.py", line 380, in get
    self.model._meta.object_name
db.models.DoesNotExist: BookInfo matching query does not exist.

>>> BookInfo.objects.count()
6

属性名称__比较运算符=值
# 属性名称和比较运算符间使用两个下划线，所以属性名不能包括多个下划线

BookInfo.objects.filter(id__exact=1)
可简写为：
BookInfo.objects.filter(id=1)

BookInfo.objects.filter(btitle__contains='传')

BookInfo.objects.filter(btitle__endswith='部')

以上运算符都区分大小写，在这些运算符前加上i表示不区分大小写，如iexact、icontains、istartswith、iendswith.

BookInfo.objects.filter(btitle__isnull=False)

BookInfo.objects.filter(id__in=[1, 3, 5])

BookInfo.objects.filter(id__gt=3)

BookInfo.objects.exclude(id=3)

BookInfo.objects.filter(bpub_date__year=1980)

BookInfo.objects.filter(bpub_date__gt=date(1990, 1, 1))

对象.objects.filter(属性__gte=F('属性'))

from django.db.models import F
BookInfo.objects.filter(bread__gte=F('bcomment'))

BookInfo.objects.filter(bread__gt=F('bcomment') * 2)

对象.objects.filter(Q(属性__gt=20)|Q(属性__lt=3))

from django.db.models import Q

BookInfo.objects.filter(Q(bread__gt=20)|Q(id__lt=3))

BookInfo.objects.filter(~Q(pk=3))

 {'属性名__聚合类小写':值}
  如:{'bread__sum':3}

对象.objects.aggregate(Sum('属性'))

from django.db.models import Sum

BookInfo.objects.aggregate(Sum('bread'))

BookInfo.objects.all().order_by('bread')  # 升序
BookInfo.objects.all().order_by('-bread')  # 降序

一对应的模型类对象.多对应的模型类名小写_set

b = BookInfo.objects.get(id=1)
b.heroinfo_set.all()

多对应的模型类对象.多对应的模型类中的关系类属性名

h = HeroInfo.objects.get(id=1)
h.hbook

多对应的模型类对象.关联类属性_id

h = HeroInfo.objects.get(id=1)  # HeroInfo是多的一方，hbook是定义在一的一方
h.hbook_id

关联模型类名小写__属性名__条件运算符=值

BookInfo.objects.filter(heroinfo__hname='孙悟空')

BookInfo.objects.filter(heroinfo__hcomment__contains='八')

一模型类关联属性名(FK对应属性名)__一模型类属性名__条件运算符=值

HeroInfo.objects.filter(hbook__btitle='天龙八部')

HeroInfo.objects.filter(hbook__bread__gt=30)

hero = HeroInfo.objects.get(hname='猪八戒')
hero.hname = '猪悟能'
hero.save()

HeroInfo.objects.filter(hname='沙悟净').update(hname='沙僧')

hero = HeroInfo.objects.get(id=13)
hero.delete()

HeroInfo.objects.filter(id=14).delete()