F和Q查询

# 把read_num都加1
from django.db.models import F
ret=models.Book.objects.all().update(read_num=F('read_num')+1)
print(ret)


#查询评论数大于阅读数的书籍
ret=models.Book.objects.all().filter(commit_num__gt=F('read_num'))
for i in ret:
print(i.name)

## 查询评论数大于阅读数2倍的书籍
ret=models.Book.objects.filter(commit_num__gt=F('read_num')*2)
print(ret)

from django.db.models import Q
# ret=models.Book.objects.filter(Q(name='egon') | Q(price__gt=100))
# 查询名字叫egon并且价格大于100的书
# ret=models.Book.objects.filter(Q(name='egon') & Q(price__gt=100))
# ret=models.Book.objects.filter(name='egon',price__gt=100)


# 查询名字不为egon的书
# ret = models.Book.objects.filter(~Q(name='egon'))
# print(ret)

# Q可以嵌套
ret = models.Book.objects.filter((Q(name='egon') & Q(price__lt=100)) | Q(id__lt=3))
print(ret)