1.orm commonly used commands
# models.Book.objects
# 增
create()
# 删
delete()
# 改
update()
# 查
filter()
exclude() # 与filter()取反，除条件之外的记录。
all()
get()----># 此命令可直接获取对象本身，但如果查找的记录不存在，则会报错。
# 获取queryset中的对象
first()
last()
# 其他
values() # 获取queryset中指定字段的数据，以字典形式
values_list() # 和values一样，以元组形式
count() # 计数 不接受任何参数
order_by() # 按指定字段进行排序
exists() # 判断queryset是否有数据
reverse() # 将queryset的顺序倒置，一般在order_by后使用。
distinct() # 将queryset去重（每个字段的值都必须完全一样才会被去重）2. Double underline inquiry
# 查询id>2的数据
res = models.Book.objects.filter(id__gt=2)
# 查询id>=2的数据
res = models.Book.objects.filter(id__gte=2)
# __lt、__lte 同理
# 查询在每个范围内的数据
res = models.Book.objects.filter(id__in=[1,2,3])
res = models.Book.objects.filter(id__in=range(1,6,2))
# 查询在100-1000价格的数据，包括10和100
res = models.Book.objects.filter(price__range=(100,1000))
# 模糊查询
res = models.Book.objects.filter(title__contains='三')
# 不区分大小写icontains
res = models.Book.objects.filter(title__icontains='三')
# 查询2020年1月出版的电影
res = models.Book.objects.filter(publish_date_year=2020,publish_date_month=1)3. deletions foreign key column change search
# 一对多 在book表增加一条数据
# 方式1
models.Book.objects.create(title='三国演义',price=333,publish_id=1)
# 方式2：通过增加或查找先得到一个obj对象
publish_obj = models.Publish.objects.create(name='东方出版社',addr='东京')
models.Book.objects.create(title='三国演义',price=333,publish=publish_obj)
# 对book表中的外键字段进行修改
models.Book.objects.filter(pk=1).update(publish_id=2)
# 将id为1的book出版社改为东方出版社
publish_obj = models.Publish.objects.filter(name='东方出版社').first()
models.Book.objects.filter(pk=1).update(publish=publish_obj)When you create a record for the many to many association, due django orm is the third table is automatically created for us, our models class does not exist in this category. So we can not directly targeted at the third table to add an association record book and the author.
It can only be added by means of the associated record in the book _obj and author_obj.
# 多对多 add、remove、set、clear
# 1.给书籍绑定作者关系
book_obj = models.Book.objects.filter(pk=1).first()
res = book_obj.author.all() # 可获得book_obj这条记录对应的作者对象。本质上在book_obj.author时进行了与book_author的连表操作，并获取到了结果。
# 为书籍与作者id为2和3进行绑定。
book_obj.author.append(2,3)
# 为某一书籍与作者david4和david3进行绑定
book_obj = models.Book.objects.filter(pk=1).first()
res = book_obj.author.all()
print(res)
print(res.query)
author_obj1 = models.Author.objects.filter(name='David4').first()
author_obj2 = models.Author.objects.filter(name='David3').first()
book_obj.author.add(author_obj1,author_obj2)
#remove方法与add方法同理
#set方法:接收一个元组或列表，有则删除、无则添加。
book_obj.author.set((1,))
# clear方法无需参数
book_obj.author.clear()4. Cross-table query
Cross-table query into sub-queries and linked tables query.
Subquery : query results as a table in another query a table.
Union-table query : First two associated table merge, and then query.
Sub-queries and linked tables and queries have a forward lookup reverse lookup concept.
Forward query : Cross-table query when the foreign key field in the current data object is forward, when the query as a foreign key field .
Reverse Lookup : Cross-table query when the foreign key field is not in the current data object is the reverse, according to the table name in lowercase _set query.
note:! ! ! Foreign key field is absent in the current models prevail in the data object! ! ! Whether one positive and negative do not need to add _set.
# 基于对象的跨表查询（子查询）
# 1.查询书籍id为1的出版社名称
book_obj = models.Book.objects.filter(pk=1).first()
# res = models.Publish.objects.filter(pk=book_obj.publish_id)
# print(res.first().name)
res = book_obj.publish.name
print(res)
#2.查询书籍id为2的所有作者
book_obj = models.Book.objects.filter(pk=2).first()
res = book_obj.author.all()
print(res)
#3.查询作者id为1的电话号码
author_obj = models.Author.objects.filter(id=1).first()
res = author_obj.author_detail
print(res.phone)
#4.查询出版社名称为东方出版社的书籍
publish_obj = models.Publish.objects.filter(name='东方出版社').first()
res = publish_obj.book_set.all()
print(res)
#5.查询作者为david1的书籍
author_obj = models.Author.objects.filter(name='David1').first()
res = author_obj.book_set.all()
print(res)
#6.查询手机号为110的作者
author_detail_obj = models.AuthorDetails.objects.filter(phone=110).first()
res = author_detail_obj.author
print(res)# 基于双下划线跨表查询(联表查询)
# django会将__自动识别为联表
# 1、查询书籍id为1的出版社名称
# 正向查询
res = models.Book.objects.filter(id=1).values('publish__name')
print(res)
# 反向查询
res = models.Publish.objects.filter(book__id=1)
print(res)
# 2.查询书籍id为1的作者姓名和年龄
# 正向查询
res = models.Book.objects.filter(id=1).values('author__name','author__age')
# 反向查询
res = models.Author.objects.filter(book__id=1)
print(res)
# 3.查询作者是David1的年龄和手机号
# 正向查询
res = models.Author.objects.filter(name='David1').values('name','age','author_detail__phone')
print(res)
# 反向查询
res = models.AuthorDetails.objects.filter(author__name='David1')
print(res.first().phone)
# 4.查询书籍id为1的作者的手机号
# 正向查询
res = models.Book.objects.filter(pk=1).values('author__author_detail__phone')
print(res)
# 反向查询
res = models.AuthorDetails.objects.filter(author__book__id=1)
print(res.first().phone)
#！！！！！ 只要表之间有关系，就可以一直用__进行联表操作。！！！！！！！The aggregate query
Keywords aggregate
from django.db.models import Max, Min, Avg, Count, Sum
# 查询所有书的平均价格
res = models.Book.objects.aggregate(avg_num=Avg('price'))
print(res)
# 查询最贵的书的价格
res = models.Book.objects.aggregate(max_price=Max('price'))
print(res)
res = models.Book.objects.aggregate(Avg("price"),Max("price"), Min("price"),Count("pk"),Sum('price'))
print(res)6. grouping queries
Keywords annotate
from django.db.models import Max, Min, Avg, Count, Sum
# 1.统计每一本数的作者的个数
res = models.Book.objects.all().annotate(author_num=Count('author')).values('title','author_num')
print(res)
# 2.统计出每个出版社卖的最便宜的书的价格
res = models.Publish.objects.all().annotate(min_price=Min('book__price')).values('name','min_price')
print(res)
#3.统计出不止一个作者的书
res =models.Book.objects.annotate(author_num=Count('author__id')).filter(author_num__gt=1)
print(res)
# 4.查询各个作者出的书总价格
res = models.Author.objects.annotate(total_price=Sum('book__price')).values('name','total_price')
print(res)
# 按照表中的一个字段分组
res = models.Book.objects.values('price').annotate()7.F queries and query Q
from django.db.models import F,Q
# F可以获取到每条记录对应的字段值
# 1.查询库存数大于销售数的书籍
res = models.Book.objects.filter(storage__gt=F('sales'))
print(res)
# 2. 为所有书籍价格增加100
res = models.Book.objects.update(price=F('price') + 100)
print(res)
# Q的用法
q = Q()
q.connector = 'or' # q对象默认也是and关系 可以通过connector改变or
q.children.append(('title','python入门'))
q.children.append(('price',1000))
res = models.Book.objects.filter(q)
print(res)