django的ORM基础操作

'''ORM基础操作'''

'''orm返回的两种数据类型： 1.QuerySet 2.object'''
'''1.QuerySet'''
# 支持链式编程，可以在all后面加方法
qs = models.Teacher.objects.all() #获取全部 Teacher数据qs,返回的是QuerySet
name = qs.values('name')  #通过value字段进行过滤,获取我们希望获取到的字段
print(name)  #返回QuerySet
count = qs.count()  #获取qs的个数
print(count)
firstData = qs.first() #获取qs的第一个数据，等同于list[0]
print(firstData)  #返回的是object
valueList = qs.values_list('name') #只获取数据中的value
print(valueList)  #返回QuerySet

'''2.object'''
teacher = models.Teacher.objects.get(id=1)  #返回的是object
print(teacher.name)
teacher = models.Teacher.objects.first()  #只获取第一个数据obj
name = teacher.name  #获取其中一个字段
teacher = models.Teacher.objects.raw('select * from teacher;')  #执行原生sql  qs

'''过滤 orm filter sql的where条件'''
teacher = models.Teacher.objects.filter(name__contains='吴')  #过滤，模糊查询, ==sql中%
print(teacher)
teacher = models.Teacher.objects.filter(name__endswith='牛')  #过滤，以什么结尾
print(teacher)
teacher = models.Teacher.objects.filter(name__startswith='牛')  #过滤，以什么开始
print(teacher)
teacher = models.Teacher.objects.filter(name__in=['冯璐','牛牛'])  #过滤，在什么范围内 ==sql的in条件
print(teacher)
teacher = models.Teacher.objects.filter(name__in=['冯璐','牛牛1'])  #过滤，在什么范围内 ==sql的in条件
print(teacher)
teacher = models.Teacher.objects.filter(name_isnull=True)  #过滤，为空
teacher = models.Teacher.objects.filter(id__gt=1)  #过滤，大于
print(teacher)
teacher = models.Teacher.objects.filter(id__gte=1)  #过滤，大于等于
print(teacher)
teacher = models.Teacher.objects.filter(id__lt=1)  #过滤，小于
print(teacher)
teacher = models.Teacher.objects.filter(id__lte=1)  #过滤，小于等于
print(teacher)
teacher = models.Teacher.objects.filter(id__range=[1,4])  #过滤，在1到4之间  between  and，包括4
print(teacher)

'''排除，排除的方法和上面的filter是一样的'''
teacher = models.Teacher.objects.exclude(id__gt=2)  #排除id大于2的  其他用法和filter相同
print(teacher)
teacher = models.Teacher.objects.exclude(name='牛牛')
print(teacher)

'''多条件查询'''
# and操作
teacher = models.Teacher.objects.filter(id=1,name='牛牛') #where id=1 and name='牛牛'
print(teacher)

# or操作
# 通过django中提供的q来实现负责的过滤
# 导入 from django.db.models import Q
teacher =models.Teacher.objects.filter(Q(name='大师兄')&Q(id=4))  #&相当于sql中的and
print(teacher)
teacher =models.Teacher.objects.filter(Q(name='大师兄')|Q(id=2))  #&相当于sql中的or
print(teacher)
# 在 Q前面可以通过~取反，代表name!=大师兄 and id=2
teacher =models.Teacher.objects.filter(~Q(name='大师兄')&Q(id=2))
print(teacher)
# 使用Q之外，还可以使用关键字参数，再次进行过滤，Q必须写在关键字参数的前面
teacher =models.Teacher.objects.filter(~Q(name='大师兄')&Q(id=3),name__contains='吴')
print(teacher)