from django.db import models
class Question(models.Model):
text = models.CharField(max_length=200)
pub_date = models.DateTimeField('published_date')
def __unicode__(self):
return self.text
先在 settings.py 中进行设置：
TIME_ZONE = 'Asia/Shanghai'
LANGUAGE_CODE = 'zh-CN'
然后创建一些数据：
>>> Question.objects.create(
text='what are you doing',
pub_date=datetime.datetime(2015, 11, 7)
)
>>> Question.objects.create(
text='what is wrong with you',
pub_date=datetime.datetime(2014, 11, 7)
)
>>> Question.objects.create(
text='who are you',
pub_date=datetime.datetime(2015, 10, 7)
)
>>> Question.objects.create(
text='who am i',
pub_date=datetime.datetime(2014, 10, 7)
)
>>> Question.objects.all()
[<Question: what are you doing>, <Question: what is wrong with you>, <Question: who are you>, <Question: who am i>]
AND
将多个 Q 对象作为非关键字参数或使用 & 联结即可实现 AND 查询：
>>> from django.db.models import Q
# Q(...)
>>> Question.objects.filter(Q(text__contains = 'you'))
[<Question: what are you doing>, <Question: what is wrong with you>, <Question: who are you>]
# Q(...), Q(...)
>>> Question.objects.filter(Q(text__contains = 'you'), Q(text__contains = 'what'))
[<Question: what are you doing>, <Question: what is wrong with you>]
# Q(...) & Q(...)
>>> Question.objects.filter(Q(text__contains = 'you') & Q(text__contains = 'what'))
[<Question: what are you doing>, <Question: what is wrong with you>]
OR
使用 | 联结两个 Q 对象即可实现 OR 查询：
# Q(...) | Q(...)
>>> Question.objects.filter(Q(text__contains = 'you') | Q(text__contains = 'who'))
[<Question: what are you doing>, <Question: what is wrong with you>, <Question: who are you>, <Question: who am i>]
NOT
使用 ~ 即可实现 NOT 查询：
# ~Q(...)
>>> Question.objects.filter(~Q(text__contains = 'you'))
[<Question: who am i>]
扩展：
想按条件过滤掉某些数据，如何表示“不等于”这个概念呢？
>>> Question.objects.filter(text != '')
上面这种写法是错误的，正确的写法是：
# exclude
>>> Question.objects.exclude(text = '')
[<Question: what are you doing>, <Question: what is wrong with you>, <Question: who are you>, <Question: who am i>]
# ~Q(...)
>>> Question.objects.filter(~Q(text = ''))
[<Question: what are you doing>, <Question: what is wrong with you>, <Question: who are you>, <Question: who am i>]
Q 对象与关键字参数共用
Q 对象可以结合关键字参数一起传递给查询函数，不过需要注意的是要将Q 对象放在关键字参数的前面：
# Q(...), key=value
>>> Question.objects.filter(Q(text__contains = 'you'), text__contains = 'who')
[<Question: who are you>]
OR，AND，NOT 多条件自由组合
# (A OR B) AND C AND (NOT D)
>>> Question.objects.filter((Q(text__contains = 'you') | Q(text__contains = 'who')) & Q(text__contains = 'what') & ~Q(text__contains = 'are'))
[<Question: what is wrong with you>]
动态构建查询条件
比如定义了一个包含一些 Q 对象的列表，那么如何使用这个列表构建 AND 或 OR 查询呢？ 可以使用 operator 和 reduce：
>>> import operator
>>> q_list = [Q(text__contains = 'you'), Q(text__contains = 'who')]
# OR
>>> Question.objects.filter(reduce(operator.or_, q_list))
[<Question: what are you doing>, <Question: what is wrong with you>, <Question: who are you>, <Question: who am i>]
# AND
>>> Question.objects.filter(reduce(operator.and_, q_list))
[<Question: who are you>]
这个列表也可能是根据用户的输入来构建的，比如简单的搜索功能（搜索一个文章的标题或内容或作者包含某个关键字）：
q = request.GET.get('q', '').strip()
q_list = []
if q:
for key in ['title__contains', 'content__contains', 'author__contains']:
q_list.append(Q(**{key: q}))
queryset = Entry.objects.filter(reduce(operator.or_, q_list))
