Django（六）、ORM操作进阶
前言
上一篇中，介绍了django的单表操作，本篇描述一下django的多表操作，包括条件过滤、联表操作等.
一、双下划綫条件过滤：
# 获取个数
#
# models.Tb1.objects.filter(name='seven').count()
# 大于，小于
#
# models.Tb1.objects.filter(id__gt=1) # 获取id大于1的值
# models.Tb1.objects.filter(id__gte=1) # 获取id大于等于1的值
# models.Tb1.objects.filter(id__lt=10) # 获取id小于10的值
# models.Tb1.objects.filter(id__lte=10) # 获取id小于10的值
# models.Tb1.objects.filter(id__lt=10, id__gt=1) # 获取id大于1 且 小于10的值
# in
#
# models.Tb1.objects.filter(id__in=[11, 22, 33]) # 获取id等于11、22、33的数据
# models.Tb1.objects.exclude(id__in=[11, 22, 33]) # not in
# isnull
# Entry.objects.filter(pub_date__isnull=True)
# contains
#
# models.Tb1.objects.filter(name__contains="ven")
# models.Tb1.objects.filter(name__icontains="ven") # icontains大小写不敏感
# models.Tb1.objects.exclude(name__icontains="ven")
# range
#
# models.Tb1.objects.filter(id__range=[1, 2]) # 范围bettwen and
# 其他类似
#
# startswith，istartswith, endswith, iendswith,
# order by
#
# models.Tb1.objects.filter(name='seven').order_by('id') # asc
# models.Tb1.objects.filter(name='seven').order_by('-id') # desc
# group by
#
# from django.db.models import Count, Min, Max, Sum
# models.Tb1.objects.filter(c1=1).values('id').annotate(c=Count('num'))
# SELECT "app01_tb1"."id", COUNT("app01_tb1"."num") AS "c" FROM "app01_tb1" WHERE "app01_tb1"."c1" = 1 GROUP BY "app01_tb1"."id"
# limit 、offset
#
# models.Tb1.objects.all()[10:20]
# regex正则匹配，iregex 不区分大小写
#
# Entry.objects.get(title__regex=r'^(An?|The) +')
# Entry.objects.get(title__iregex=r'^(an?|the) +')
# date
#
# Entry.objects.filter(pub_date__date=datetime.date(2005, 1, 1))
# Entry.objects.filter(pub_date__date__gt=datetime.date(2005, 1, 1))
# year
#
# Entry.objects.filter(pub_date__year=2005)
# Entry.objects.filter(pub_date__year__gte=2005)
# month
#
# Entry.objects.filter(pub_date__month=12)
# Entry.objects.filter(pub_date__month__gte=6)
# day
#
# Entry.objects.filter(pub_date__day=3)
# Entry.objects.filter(pub_date__day__gte=3)
# week_day
#
# Entry.objects.filter(pub_date__week_day=2)
# Entry.objects.filter(pub_date__week_day__gte=2)
# hour
#
# Event.objects.filter(timestamp__hour=23)
# Event.objects.filter(time__hour=5)
# Event.objects.filter(timestamp__hour__gte=12)
# minute
#
# Event.objects.filter(timestamp__minute=29)
# Event.objects.filter(time__minute=46)
# Event.objects.filter(timestamp__minute__gte=29)
# second
#
# Event.objects.filter(timestamp__second=31)
# Event.objects.filter(time__second=2)
# Event.objects.filter(timestamp__second__gte=31)
二、其他操作
# 执行原生SQL
#
# from django.db import connection, connections
# cursor = connection.cursor() # cursor = connections['default'].cursor()
# cursor.execute("""SELECT * from auth_user where id = %s""", [1])
# row = cursor.fetchone()三、联表操作
1.一对多
表结构如下：
class Book(models.Model):
name = models.CharField(max_length=32)
class Author(models.Model):
name = models.CharField(max_length=32)
books = models.ForeignKey(to="Book",to_field="id")查询:
#方式一
a1=models.Author.objects.filter(id=1).first()
a1.books.name #以属性的方式关联，Author类的对象通过books属性关联至Book对象，再通过.name属性获取Book对象的name字段
#方式二
res=models.Author.objects.filter(id=1).values("books_id","books__name")
print(res)
#在本地表通过ForeignKey关联，会在本地表内默认生成一个以指定属性名+'_'+'to_field字段名'的字段，例如这里会生成一个books_id字段，代指book.id字段，因此books_id不需跨表查询，books__id需跨表查询。通过双下划线，可以跨表关联字段，例如book__name字段代指book.name改:
models.Author.objects.filter(id=1).update("books":[b1,b2..])总结：
一对多操作,单对象，通过”.”属性方法方式跨表操作，queryset通过”__”跨表取字段
2.多对多
方式一：
自定义第三张表：
class Book(models.Model):
name = models.CharField(max_length=32)
class Author(models.Model):
name = models.CharField(max_length=32)
class Relation(models.Model):
b = models.ForeignKey('Book')
a= models.ForeignKey('Author')通过普通表进行反向间接查找
a1=models.Author.objects.filter(id=1).first()
obj = a1.relation_set.all()
#obj取出的是所有包含a1记录的relation类中的对象，queryset格式,使用类名+"_set"的格式时，类名字母需小写
obj1 = a1.relation_set.select_related('b').all()
#obj1取出的是所有包含a1记录通过relation类关联的Book类的对象，queryset格式
for i in obj:
print(i.b.name)
for i in obj:
print(i.name)
2 通过关系表relation进行查找
obj = models.Relation.objects.filter(a__=1).all()
for i in obj:
print(i.b.name)
通过中间关系表，相较于上面的反向查找更好理解。
方式二
只定义两张表，关系表由django自动创建维护
#models.py
class Book(models.Model):
name = models.CharField(max_length=32)
class Author(models.Model):
name = models.CharField(max_length=32)
m = models.ManyToManyField('Book')
# views.py
# ManyToManyField
obj = models.Author.objects.filter(id=1).first()
# 增
# obj.m.add(3)
# obj.m.add(3,4)
# obj.m.add(*[1,2])
# 删
# obj.m.remove(3)
# obj.m.remove(3,4)
# obj.m.remove(*[1,2])
# 改
# obj.m.set([1,2,])
#查
obj.m.all() #查出所有的关联Book对象
obj.m.all().values("id","name") #查出所有的关联Book对象的name字段
# for row obj.m.all():
# print(row.id,row.name)
#清除
# obj.m.clear()
# 反向查 在没有定义ManyToManyField 字段的表中查
b= models.Book.objects.filter(id=1).first()
b_authors = obj.author_set.all() #获取所有的对应的Author类的对象
# 反向的改
obj.author_set.set([1,2,3])
for row in girl_list:
print(row.id,row.name)总结：在没有ForeignKey或者ManyToManyField的表内反向查找时，需要使用使用类名+”_set”的格式来获取对象
one to one/maney to maney/foreign key各种混合关系查询
class HostInfo(models.Model):
host = models.OneToOneField(to=Host, verbose_name="主机", primary_key=True)
hostname = models.CharField(verbose_name="主机名", max_length=100, blank=True, null=True)
class Host(models.Model):
name = models.CharField(verbose_name="资产名", max_length=100, unique=True)
ip = models.ManyToManyField(to=IP, verbose_name="IP", blank=True)
category = models.ForeignKey(to=Category, verbose_name="分类")
class Category(models.Model):
name = models.CharField(max_length=20, verbose_name="分类")
class IP(models.Model):
address = models.CharField(verbose_name="IP地址", max_length=20)# 根据ip地址查host，hostinfo
ips = ("192.168.1.2","192.168.1.3",)
host = Host.objects.filter(ip__address__in=ips)
hostinfo = HostInfo.objects.filter(host__ip__address__in=ips)
# 根据类型查host,hostinfo
host = Host.objects.filter(category__name="physical")
hostinfo = HostInfo.objects.filter(host__category__name="physical")
# one to one单层关系正查反查：
hostinfo = HostInfo.objects.get(hostname="test")
host = hostinfo.host
host = Host.objects.get(name="company-test1")
hostinfo = host.hostinfo #onetoone反查使用反查对象类名首字母小写可获取到对象