from django.db.models import Avg,Sum,Count,Max,Min
# 1、查询所有图书的平均价格
print(models.Book.objects.all().aggregate(Avg("price")))

from django.db.models import Avg,Sum,Count,Max,Min
# 1、查询所有图书的平均价格
print(models.Book.objects.all().aggregate(avgprice = Avg("price")))

print(models.Book.objects.all().aggregate(Avg("price"),Max("price"),Min("price")))
#打印的结果是：  {'price__avg': 174.33333333333334, 'price__max': Decimal('366.00'), 'price__min': Decimal('12.00')}

    # 方式一：print(models.Book.objects.all().annotate(authorNum = Count("authorlist__name")).values("authorNum"))# 方式二：booklist =models.Book.objects.all().annotate(authorNum=Count("authorlist__name"))for book_obj in booklist:print(book_obj.title,book_obj.authorNum)

    # 2、统计每一个出版社的最便宜的书# 方式一：print(models.Book.objects.values("publish__name").annotate(nMinPrice=Min('price')))  注意：values内的字段即group by的字段，，也就是分组条件# 方式二：print(models.Publish.objects.all().annotate(minprice=Min("book__price")).values("name","minprice"))# 方式三publishlist = models.Publish.objects.annotate(minprice = Min("book__price"))for publish_obj in publishlist:print(publish_obj.name,publish_obj.minprice)

print(models.Book.objects.filter(title__startswith="py").annotate(authNum = Count("authorlist__name")).values("authNum"))

print(models.Book.objects.annotate(num_authors=Count('authorlist__name')).filter(num_authors__gt=1).values("title","num_authors"))

print(models.Book.objects.all().annotate(authorsNum=Count("authorlist__name")).order_by("authorsNum"))

 # 方式一print(models.Author.objects.all().annotate(priceSum = Sum("book__price")).values("name","priceSum"))# 方式二print(models.Book.objects.values("authorlist__name").annotate(priceSum=Sum("price")).values("authorlist__name","priceSum"))