django之多表查詢操做

基於雙下劃線的跨表查詢（連表查詢 join）

select emp.name from emp inner join dep on emp.dep_id = dep.id where dep.name='技術';
    select emp.name from dep inner join emp on emp.dep_id = dep.id where dep.name='技術';

示例:

# 一對一
# 查詢一下王洋的電話號碼

# ret = models.Author.objects.filter(name='王洋').values('au__telephone')

# ret = models.AuthorDetail.objects.filter(author__name='王洋').values('telephone')
# print(ret) #<QuerySet [{'au__telephone': '110'}]> #<QuerySet [{'telephone': '110'}]>
#

# 一對多
# 海狗的慫逼人生這本書是哪一個出版社出版的
# ret = models.Book.objects.filter(title='海狗的慫逼人生').values('publishs__name')
# print(ret) #<QuerySet [{'publishs__name': '24期出版社'}]>
# ret = models.Publish.objects.filter(book__title='海狗的慫逼人生').values('name')
# print(ret) #<QuerySet [{'name': '24期出版社'}]>


#查詢一下24期出版社出版了哪些書
# ret = models.Publish.objects.filter(name='24期出版社').values('book__title')
# print(ret) #<QuerySet [{'book__title': '華麗的產後護理'}, {'book__title': '海狗的慫逼人生'}]>

# ret = models.Book.objects.filter(publishs__name='24期出版社').values('title')
# print(ret) #<QuerySet [{'title': '華麗的產後護理'}, {'title': '海狗的慫逼人生'}]>

# 多對多
#海狗的慫逼人生 是哪些做者寫的
# ret = models.Book.objects.filter(title='海狗的慫逼人生').values('authors__name')
# print(ret)

# ret = models.Author.objects.filter(book__title='海狗的慫逼人生').values('name')
# print(ret) #<QuerySet [{'name': '王洋'}, {'name': '海狗'}]>
# return render(request,'index.txt',{'x':123,'y':456})


# related_name
# 查詢一下24期出版社出版了哪些書
ret = models.Publish.objects.filter(name='24期出版社').values('xxx__title') #xxx代替反向查詢的小寫表名
print(ret)

聚合查詢

ret = models.Book.objects.all().aggregate(a=Avg('price'),m=Max('price'))
print(ret) 
#{'price__avg': 45.1, 'price__max': Decimal('200.00')} python字典格式,也就是說,聚合查詢是orm語句的結束

分組查詢

# 每一個出版社出版的書的平均價格
    # 用的是publish表的id字段進行分組
    # ret = models.Book.objects.values('publishs__id').annotate(a=Avg('price'))
    # 用的book表的publishs_id字段進行分組
    # ret = models.Book.objects.values('publishs_id').annotate(a=Avg('price'))
    # print(ret)
    # ret = models.Publish.objects.annotate(a=Avg('book__price')).values('a')
    # print(ret) #<QuerySet [{'a': None}, {'a': 71.166667}, {'a': 6.0}]>

F查詢

from django.db.models import Avg, Sum, Max, Min, Count,F
查詢一下評論數大於點贊數的書
# ret = models.Book.objects.filter(comment__gt=F('good'))
# print(ret)


將全部書的價格上調100塊
# models.Book.objects.all().update(
#     price=F('price')+100
# )

Q查詢

from django.db.models import Avg, Sum, Max, Min, Count, F,Q
    ret = models.Book.objects.filter(Q(id=2)&Q(Q(price__gt=112)|~Q(comment__lte=200)))
    print(ret)