1，外鍵

2，多對多

3，一對一 外鍵加唯一索引

註意values查詢返回的是一個字典的queryset

查看聚合分組的源碼 所以註意分組一定要使用values

4，註意查詢表與表之間通過外鍵和多對多關系關聯。

5，ORM查詢和sql查詢邏輯相似。不同表之間查詢需要通過鍵實現。

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

def tp5(request):
    # #通過orm外鍵查詢書和作者關系
    # ret=Book.objects.values(‘title‘,‘authors__name‘)
    # print(‘=========>‘,ret)


    #單表查詢  查詢python這邊書的價格
    # ret=Book.objects.filter(title=‘python‘).values(‘pric‘)


    #註意下面是查詢是依賴的ForeignKey  ForeignKey
    # 查詢python的這邊書的出版社的聯系方式
    # ret = Book.objects.filter(title=‘python‘).values(‘publisher__address‘)
    # print(ret)

    #查詢python的所有作者名字
    # ret=Book.objects.filter(title=‘python‘).values(‘authors__name‘)
    # print(ret)


    #查詢alex出版的所有書的name
    ret=Book.objects.filter(authors__name=‘alex‘).values(‘title‘)
    print(ret)


    #反向查詢
    ret=author.objects.filter(name=‘alex‘).values(‘book__title‘)
    print(‘反向查詢‘,ret)


    ret=Book.objects.first()
    print(ret.title)
    print(‘==========‘,ret)
    ret=Book.objects.filter(title=‘python‘).values(‘publisher__name‘)
    print(ret)

#####aggregate對queryset進行統計
    ret=Book.objects.all().aggregate(sum=Sum(‘pric‘))
    print(ret)
    ret = Book.objects.all().aggregate(count=Count(‘title‘))
    print(ret)

    #select AVG(pric) from book;
    ret=Book.objects.all().aggregate(pric=Avg(‘pric‘),maxpric=Max(‘pric‘))
    print(ret)

    # ret=Book.objects.filter(title=‘python‘).values(‘authors__name‘)
    # print(ret)

####分組查詢annotate對分組後的queryset值進行操作
    ret=Book.objects.filter(authors__name=‘alex‘).aggregate(Sum(‘pric‘))
    print(ret)

    ret=author.objects.filter(name=‘alex‘).aggregate(Sum(‘book__pric‘))
    print(‘dddddd‘,ret)
    print(‘@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@‘)
    #每個作者出的書的總價格
    ret=Book.objects.values(‘authors__name‘).annotate(pric=Sum(‘pric‘))
    print(‘分組‘,ret)
    print(‘#######################‘)


    ##自動通過第三張表完成作者和書的關系查詢
    ret = Book.objects.values(‘authors__name‘)
    print(ret)

    #自動通過外鍵完成了書和出版社的關系查詢
    ret=Book.objects.values(‘title‘,‘publisher__name‘)
    print(‘書和出版社的關系‘,ret)



##註意聚合和分組的查詢都是對queryset
    ret=Book.objects.values(‘authors__name‘).annotate(Sum(‘pric‘))

    print(ret)
    return HttpResponse(‘執行成功‘)

def tp6(request):

    ret=Book.objects.values().aggregate(Avg(‘pric‘),Max(‘pric‘))
    print(ret)

    ret=author.objects.filter(name=‘alex‘).aggregate(Sum(‘book__pric‘))
    print(ret)


    ret=Book.objects.filter(authors__name=‘alex‘).aggregate(Sum(‘pric‘))
    print(ret)


    #OrderedDict通過對字典元素排序
    ret=Book.objects.values(‘authors__name‘).annotate(Sum(‘pric‘))
    print(ret)



    return HttpResponse(‘執行成功‘)


def tp7(request):
    ‘‘‘
    F查詢  F就是之前的值
    Q查詢  Q可以多層嵌套
    Q查詢   與或非
            &  |   ~
    :param request:
    :return:
    ‘‘‘
    # Book.objects.update(pric=F(‘pric‘)+20)

    ret=Book.objects.filter(
        Q(title__startswith=‘p‘)|Q(title__startswith=‘l‘)
    ).first()
    print(ret)

    ret = Book.objects.filter(
        Q(Q(pric__lt=300)&Q(pric__gt=270))
    )
    print(‘dddddddddddddd‘,ret)
    Book.objects.filter(title=‘python‘).delete()
    return HttpResponse(‘執行成功‘)

ORM操作(一)