三种关系:一对一,一对多,多对多
创建表
一对一 xx = models.OneToOneField(to='表名',to_field='字段名',on_delete=models.CASCADE) #删除时的一些级联效果,to_field可以不写,默认是关联到另一张表的主键,on_delete在1.x版本的django中不用写,默认是级联删除的,2.x版本的django要写. 一对多 xx = models.ForeignKey(to='表名',to_field='字段名',on_delete=models.CASCADE) 多对多 xx = models.ManyToManyField(to='另外一个表名') #这是自动创建第三表 示例 from django.db import models # Create your models here. from django.db import models # Create your models here. #作者表 class Author(models.Model): #比较常用的信息放到这个表里面 name=models.CharField( max_length=32) age=models.IntegerField() # authorDetail=models.OneToOneField(to="AuthorDetail",to_field="nid",on_delete=models.CASCADE) authorDetail=models.OneToOneField(to='AuthorDetail') #一对一到AuthorDetail表 生成为表字段之后,会自动变为authorDetail_id这样有一个名称 # 外键字段 -- 外键字段名_id # foreign+unique def __str__(self): return self.name #作者详细信息表 class AuthorDetail(models.Model): birthday=models.DateField() # telephone=models.BigIntegerField() telephone=models.CharField(max_length=32) addr=models.CharField( max_length=64) def __str__(self): return self.addr #出版社表 和 书籍表 是 一对多的关系 class Publish(models.Model): name=models.CharField( max_length=32) city=models.CharField( max_length=32) email=models.EmailField() #charfield -- asdfasdf def __str__(self): return self.name #书籍表 class Book(models.Model): nid = models.AutoField(primary_key=True) title = models.CharField( max_length=32) publishDate=models.DateField() price=models.DecimalField(max_digits=5,decimal_places=2) #decimal(16,2) publishs=models.ForeignKey(to="Publish") authors=models.ManyToManyField(to='Author',) def __str__(self): return self.title #手动创建第三张表,暂时忽略 # class BookToAuthor(models.Model): # book_id = models.ForeignKey(to='Book') # author_id = models.ForeignKey(to='Author') # # xx = models.CharField(max_length=12)
增删改查
增
#1 增 #1.1 一对一增加 # new_author_detail = models.AuthorDetail.objects.create( # birthday='1979-08-08', # telephone='138383838', # addr='黑龙江哈尔滨' # ) # obj = models.AuthorDetail.objects.filter(addr='山西临汾').first() #方式1 # models.Author.objects.create( # name='王涛', # age='40', # authorDetail=new_author_detail, # ) # 方式2 常用 # models.Author.objects.create( # name='王涛', # age='40', # authorDetail_id=obj.id, # ) # 一对多 #方式1 # obj = models.Publish.objects.get(id=2) # models.Book.objects.create( # title = '李帅的床头故事', # publishDate='2019-07-22', # price=3, # # publishs=models.Publish.objects.get(id=1), # publishs=obj, # # ) # 方式2 常用 # models.Book.objects.create( # title='李帅的床头故事2', # publishDate='2019-07-21', # price=3.5, # # publishs=models.Publish.objects.get(id=1), # publishs_id=obj.id # # ) # 多对多 # 方式1 常用 # book_obj = models.Book.objects.get(nid=1) # book_obj.authors.add(*[1,2]) # 方式2 # author1 = models.Author.objects.get(id=1) # author2 = models.Author.objects.get(id=3) # book_obj = models.Book.objects.get(nid=5) # book_obj.authors.add(*[author1,author2])
删
一对一和一对多的删除和单表删除是一样的 # 一对一 表一外键关联到表二,表一删除,不影响表2,表2删除会影响表1 # models.AuthorDetail.objects.get(id=2).delete() # models.Author.objects.get(id=3).delete() # 一对多 # models.Publish.objects.get(id=1).delete() # models.Book.objects.get(nid=1).delete() # 多对多关系删除 # book_obj = models.Book.objects.get(nid=6) # book_obj.authors.remove(6) # book_obj.authors.remove(*[5,6]) # book_obj.authors.clear() # book_obj.authors.add(*[1,]) # book_obj.authors.set('1') # book_obj.authors.set(['5','6']) #删除然后更新
更新
# 更新 # 一对一 # models.Author.objects.filter(id=5).update( # name='崔老师', # age=16, # # authorDetail=models.AuthorDetail.objects.get(id=5), # authorDetail_id=4, # ) #一对多 # models.Book.objects.filter(pk=4).update( # title='B哥的往事2', # # publishs=models.Publish.objects.get(id=3), # publishs_id=3, # ) #一对多 models.Publish.objects.filter(pk=2).update( id=4, # 没有级联更新,报错!! )
正向查询和反向查询
关系属性(字段)写在哪个类(表)里面,从当前类(表)的数据去查询它关联类(表)的数据叫做正向查询,反之叫做反向查询
#查询 # 一对一 # 正向查询 #1 查询崔老师的电话号 # author_obj = models.Author.objects.filter(name='崔老师').first() # # print(author_obj.authorDetail) #辽宁峨眉山 # # print(author_obj.authorDetail.telephone) #444 # #2 反向查询 # #2 查询一下这个444电话号是谁的. # author_detail_obj = models.AuthorDetail.objects.get(telephone='444') # print(author_detail_obj.author) #崔老师 # print(author_detail_obj.author.name) #崔老师 ''' 正向查询:Authorobj.authorDetail,对象.关联属性名称 Author----------------------------------->AuthorDetail <----------------------------------- 反向查询:AuthorDetailobj.author ,对象.小写类名 ''' # 一对多 # 查询一下李帅的床头故事这本书的出版社是哪个 # 正向查询 book_obj = models.Book.objects.get(title='李帅的床头故事') print(book_obj.publishs) #B哥出版社 print(book_obj.publishs.name) #B哥出版社 # B哥出版社出版社出版了哪些书 # 反向查询 pub_obj = models.Publish.objects.get(name='B哥出版社') print(pub_obj.book_set.all()) #<QuerySet [<Book: 李帅的床头故事>, <Book: 李帅的床头故事2>]> ''' 正向查询 book_obj.publishs 对象.属性 Book ---------------------------------------------> Publish <---------------------------------------------- 反向查询 publish_obj.book_set.all() 对象.表名小写_set ''' # 多对多 # 李帅的床头故事这本书是谁写的 # 正向查询 book_obj = models.Book.objects.get(title='李帅的床头故事') print(book_obj.authors.all()) # 高杰写了哪些书 author_obj = models.Author.objects.get(name='高杰') print(author_obj.book_set.all()) ''' 正向查询 book_obj.authors.all() 对象.属性 Book ---------------------------------------------> Author <---------------------------------------------- 反向查询 author_obj.book_set.all() 对象.表名小写_set '''
正向查询和反向查询
#查询 # 一对一 # 1. 查询崔老师的电话号 # 方式1 正向查询 # obj = models.Author.objects.filter(name='崔老师').values('authorDetail__telephone') # print(obj) #<QuerySet [{'authorDetail__telephone': '444'}]> # 方式2 反向查询 # obj = models.AuthorDetail.objects.filter(author__name='崔老师').values('telephone','author__age') # print(obj) #<QuerySet [{'telephone': '444'}]> # 2. 哪个老师的电话是444 # 正向 # obj = models.Author.objects.filter(authorDetail__telephone='444').values('name') # print(obj) # 反向 # obj = models.AuthorDetail.objects.filter(telephone='444').values('author__name') # print(obj) # 一对多 # 查询一下李帅的床头故事这本书的出版社是哪个 # obj = models.Book.objects.filter(title='李帅的床头故事').values('publishs__name') # print(obj) #<QuerySet [{'publishs__name': 'B哥出版社'}]> # obj = models.Publish.objects.filter(book__title='李帅的床头故事').values('name') # obj = models.Publish.objects.filter(xx__title='李帅的床头故事').values('name') # print(obj) # B哥出版社出版社出版了哪些书 # obj = models.Publish.objects.filter(name='B哥出版社').values('book__title') # print(obj) #<QuerySet [{'book__title': '李帅的床头故事'}, {'book__title': '李帅的床头故事2'}]> # obj = models.Book.objects.filter(publishs__name='B哥出版社').values('title') # print(obj) #<QuerySet [{'title': '李帅的床头故事'}, {'title': '李帅的床头故事2'}]> # 李帅的床头故事这本书是谁写的 # obj = models.Book.objects.filter(title='李帅的床头故事').values('authors__name') # print(obj) # obj = models.Author.objects.filter(book__title='李帅的床头故事').values('name') # print(obj) #<QuerySet [{'name': '高杰'}, {'name': '崔老师'}]> #高杰写了哪些书 # obj = models.Book.objects.filter(authors__name='高杰').values('title') # print(obj) # obj = models.Author.objects.filter(name='高杰').values('book__title') # print(obj) #进阶的 # B哥出版社 出版的书的名称以及作者的名字 # obj = models.Book.objects.filter(publishs__name='B哥出版社').values('title','authors__name') # print(obj) #<QuerySet [{'title': '李帅的床头故事', 'authors__name': '高杰'}, {'title': '李帅的床头故事', 'authors__name': '崔老师'}, {'title': '李帅的床头故事2', 'authors__name': '崔老师'},
{'title': '李帅的床头故事2', 'authors__name': '王涛'}]> ''' SELECT app01_book.title,app01_author.name from app01_publish INNER JOIN app01_book on app01_publish.id=app01_book.publishs_id INNER JOIN app01_book_authors on app01_book.nid = app01_book_authors.book_id INNER JOIN app01_author ON app01_author.id = app01_book_authors.author_id where app01_publish.name='B哥出版社'; :param request: :return: ''' # obj = models.Publish.objects.filter(name='B哥出版社').values('book__title','book__authors__name') # print(obj) # obj = models.Author.objects.filter(book__publishs__name='B哥出版社').values('name','book__title') # print(obj) # authorDetail author book publish # 手机号以4开头的作者出版过的所有书籍名称以及出版社名称 # ret = models.AuthorDetail.objects.filter(telephone__startswith='4').values('author__book__title','author__book__publishs__name') # print(ret) #QuerySet [{'author__book__title': '李帅的床头故事', 'author__book__publishs__name': 'B哥出版社'}, {'author__book__title': '李帅的床头故事2', 'author__book__publishs__name': 'B哥出版社'}]> #查询一下B哥出版社出版了哪些书 # obj = models.Publish.objects.filter(name='B哥出版社').first() # print(obj.xx.all())
聚合
from django.db.models import Avg,Max,Min,Sum,Count # 计算所有图书的平均价格 # obj = models.Book.objects.all().aggregate(a=Avg('price'),m=Max('price')) #aggregate()是QuerySet 的一个终止子句,得到的是个字典. # print(obj['m'] - 2) #{'price__avg': 2.833333}
分组
annotate # models.Publish.objects.annotate(a=Avg('book__price')).values('a') # models.Book.objects.values('publish_id','id').annotate(a=Avg('price')) {'pulish_id':1,'a':11.11}
F查询和Q查询
from django.db.models import F,Q F 针对自己单表中字段的比较和处理 models.Book.objects.filter(good__gt=F('comment')*2) models.Book.objects.all().update(price=F('price')+1) Q & | 非~ filter(Q(xx=11)|Q(ss=22)&Q(oo=33)) filter(Q(Q(xx=11)|Q(ss=22))&Q(oo=33)) &优先级高 filter(Q(Q(xx=11)|Q(ss=22))&Q(oo=33),name='dd')
执行原生sql(了解)
models.Publish.objects.raw('原生sql') from django.db import connection cursor = connection.cursor() cursor.excute(sql,[1,]) cursor.fetchall()
展示sql的
models.Book.objects.filter(good__gt=F('comment')*2) from django.db import connection print(connection.queries)