# 得到是queryset对象
all()         # 查询所有结果
filter()      # 过滤
exclude()     # 排除
values()      # 以字典的形式储存在对象列表里
values_list() # 以字典中的值的形式数据存放在元组里
order_by() # 排序
reverse()  # 翻转
distinct() #从返回结果中剔除重复纪录
# 得到的是对象：
get()    # 返回与所给筛选条件相匹配的对象，返回结果有且只有一个，如果符合筛选条件的对象超过一个或者没有都会抛出错误。
first()  # 返回第一条记录
last()   # 返回最后一条记录

# 其他：    
count()  # 返回数据库中匹配查询(QuerySet)的对象数量。
exists() # 返回布尔值

models.Tb1.objects.filter(id__lt=10, id__gt=1)   # 获取id大于1 且 小于10的值
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
models.Tb1.objects.filter(name__contains="ven")  # 获取name字段包含"ven"的
models.Tb1.objects.filter(name__icontains="ven") # icontains大小写不敏感
 
models.Tb1.objects.filter(id__range=[1, 3])      # id范围是1到3的，等价于SQL的bettwen and
类似的还有：startswith，istartswith, endswith, iendswith　
date字段还可以：
models.Class.objects.filter(first_day__year=2017)

class Book(models.Model):
    name = models.CharField(verbose_name=‘书名‘, max_length=32)
    pubs = models.ForeignKey(‘Publisher‘, related_name=‘book‘)

    def __str__(self): 
        return self.name


class Publisher(models.Model):
    name = models.CharField(verbose_name=‘出版社名称‘, max_length=32,unique=True)

    def __str__(self):
        return self.name

book_obj = models.Book.objects.filter(name=‘西游记‘).first()
print(book_obj.pubs.name)

# 结果：北大出版社

pub_obj = models.Book.objects.filter(pubs__name=‘北大出版社‘).first()
print(pub_obj.name)

# 结果：西游记

pub_obj = models.Publisher.objects.filter(name=‘北大出版社‘).first()
# print(pub_obj.book_set.filter(name=‘西游记‘))因为在Book表的外键字典中设置了related_name，所以直接用related_name查询，否则以这种方式查找。
print(pub_obj.book.filter(name=‘西游记‘)) 

# 结果：<QuerySet [<Book: 西游记>]>

pub_obj = models.Publisher.objects.filter(book__name=‘西游记‘).first()
print(pub_obj)

# 结果：北大出版社

from django.db.models import Avg, Sum, Max, Min, Count

from django.db.models import Avg, Sum, Max, Min, Count
models.Book.objects.all().aggregate(Avg("price"))

# 结果：{‘price__avg‘: 13.233333}

models.Book.objects.aggregate(average_price=Avg(‘price‘))

# 结果：{‘average_price‘: 13.233333}

models.Book.objects.all().aggregate(Avg("price"), Max("price"), Min("price"))
# 结果： {‘price__avg‘: 13.233333, ‘price__max‘: Decimal(‘19.90‘), ‘price__min‘: Decimal(‘9.90‘)}

select dept,AVG(salary) from employee group by dept;

from django.db.models import Avg
Employee.objects.values("dept").annotate(avg=Avg("salary").values("dept", "avg")

select dept.name,AVG(salary) from employee inner join dept on (employee.dept_id=dept.id) group by dept_id;

from django.db.models import Avg
models.Dept.objects.annotate(avg=Avg("employee__salary")).values("name", "avg")

>>> book_list = models.Book.objects.all().annotate(author_num=Count("author"))
>>> for obj in book_list:
...     print(obj.author_num)
...
2
1
1

>>> publisher_list = models.Publisher.objects.annotate(min_price=Min("book__price"))
>>> for obj in publisher_list:
...     print(obj.min_price)
...     
9.90
19.90

>>> models.Book.objects.values("publisher__name").annotate(min_price=Min("price"))
<QuerySet [{‘publisher__name‘: ‘沙河出版社‘, ‘min_price‘: Decimal(‘9.90‘)}, {‘publisher__name‘: ‘人民出版社‘, ‘min_price‘: Decimal(‘19.90‘)}]>

>>> models.Book.objects.annotate(author_num=Count("author")).filter(author_num__gt=1)
<QuerySet [<Book: 番茄物语>]>

>>> models.Book.objects.annotate(author_num=Count("author")).order_by("author_num")
<QuerySet [<Book: 香蕉物语>, <Book: 橘子物语>, <Book: 番茄物语>]>

>>> models.Author.objects.annotate(sum_price=Sum("book__price")).values("name", "sum_price")
<QuerySet [{‘name‘: ‘小精灵‘, ‘sum_price‘: Decimal(‘9.90‘)}, {‘name‘: ‘小仙女‘, ‘sum_price‘: Decimal(‘29.80‘)}, {‘name‘: ‘小魔女‘, ‘sum_price‘: Decimal(‘9.90‘)}]>

from django.db.models import F
models.Book.objects.filter(commnet_num__gt=F(‘keep_num‘))

models.Book.objects.filter(commnet_num__lt=F(‘keep_num‘)*2)

models.Book.objects.all().update(price=F("price")+30)

models.Book.objects.filter(Q(authors__name="小仙女")|Q(authors__name="小魔女"))

>>> models.Book.objects.filter(Q(author__name="小仙女") & ~Q(publish_date__year=2018)).values_list("title")
<QuerySet [(‘番茄物语‘,)]>

>>> models.Book.objects.filter(Q(publish_date__year=2018) | Q(publish_date__year=2017), title__icontains="物语")
<QuerySet [<Book: 番茄物语>, <Book: 香蕉物语>, <Book: 橘子物语>]>

import os

if __name__ == ‘__main__‘:
    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "BMS.settings")
    import django
    django.setup()

    import datetime
    from app01 import models

    try:
        from django.db import transaction
        with transaction.atomic():
            new_publisher = models.Publisher.objects.create(name="火星出版社")
            models.Book.objects.create(title="橘子物语", publish_date=datetime.date.today(), publisher_id=10)  # 指定一个不存在的出版社id
    except Exception as e:
        print(str(e))

# extra
# 在QuerySet的基础上继续执行子语句
# extra(self, select=None, where=None, params=None, tables=None, order_by=None, select_params=None)

# select和select_params是一组，where和params是一组，tables用来设置from哪个表
# Entry.objects.extra(select={‘new_id‘: "select col from sometable where othercol > %s"}, select_params=(1,))
# Entry.objects.extra(where=[‘headline=%s‘], params=[‘Lennon‘])
# Entry.objects.extra(where=["foo=‘a‘ OR bar = ‘a‘", "baz = ‘a‘"])
# Entry.objects.extra(select={‘new_id‘: "select id from tb where id > %s"}, select_params=(1,), order_by=[‘-nid‘])

举个例子：
models.UserInfo.objects.extra(
                    select={‘newid‘:‘select count(1) from app01_usertype where id>%s‘},
                    select_params=[1,],
                    where = [‘age>%s‘],
                    params=[18,],
                    order_by=[‘-age‘],
                    tables=[‘app01_usertype‘]
                )
                """
                select 
                    app01_userinfo.id,
                    (select count(1) from app01_usertype where id>1) as newid
                from app01_userinfo,app01_usertype
                where 
                    app01_userinfo.age > 18
                order by 
                    app01_userinfo.age desc
                """


# 执行原生SQL
# 更高灵活度的方式执行原生SQL语句
# 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()

LOGGING = {
    ‘version‘: 1,
    ‘disable_existing_loggers‘: False,
    ‘handlers‘: {
        ‘console‘:{
            ‘level‘:‘DEBUG‘,
            ‘class‘:‘logging.StreamHandler‘,
        },
    },
    ‘loggers‘: {
        ‘django.db.backends‘: {
            ‘handlers‘: [‘console‘],
            ‘propagate‘: True,
            ‘level‘:‘DEBUG‘,
        },
    }
}

import os

if __name__ == ‘__main__‘:
    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "BMS.settings")  # 复制 manage.py文件中环境设置
    import django
    django.setup()

    from app01 import models

    books = models.Book.objects.all()
    print(books)