Django基礎五之django模型層(二)多表操作
阿新 • • 發佈：2020-07-28
三種關係:一對一,一對多,多對多
建立表
一對一 xx = models.OneToOneField(to='表名',to_field='欄位名',on_delete=models.CASCADE) #刪除時的一些級聯效果,to_field可以不寫,預設是關聯到另一張表的主鍵,on_delete在1.x版本的django中不用寫,預設是級聯刪除的,2.x版本的django要寫. 一對多 xx = models.ForeignKey(to='表名',to_field='欄位名',on_delete=models.CASCADE) 多對多 xx = models.ManyToManyField(to='另外一個表名') #這是自動建立第三表 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): #比較常用的資訊放到這個表裡面 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') #一對一到AuthorDetail表 生成為表字段之後,會自動變為authorDetail_id這樣有一個名稱 # 外來鍵欄位 -- 外來鍵欄位名_id # foreign+unique def __str__(self): return self.name #作者詳細資訊表 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 書籍表 是 一對多的關係 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 #書籍表 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 #手動建立第三張表,暫時忽略 # class BookToAuthor(models.Model): # book_id = models.ForeignKey(to='Book') # author_id = models.ForeignKey(to='Author') # # xx = models.CharField(max_length=12)
增刪改查
增
#1 增 #1.1 一對一增加 # new_author_detail = models.AuthorDetail.objects.create( # birthday='1979-08-08', # telephone='138383838', # addr='黑龍江哈爾濱' # ) # obj = models.AuthorDetail.objects.filter(addr='山西臨汾').first() #方式1 # models.Author.objects.create( # name='王濤', # age='40', # authorDetail=new_author_detail, # ) # 方式2 常用 # models.Author.objects.create( # name='王濤', # age='40', # authorDetail_id=obj.id, # ) # 一對多 #方式1 # obj = models.Publish.objects.get(id=2) # models.Book.objects.create( # title = '李帥的床頭故事', # 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='李帥的床頭故事2', # publishDate='2019-07-21', # price=3.5, # # publishs=models.Publish.objects.get(id=1), # publishs_id=obj.id # # ) # 多對多 # 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])
刪
一對一和一對多的刪除和單表刪除是一樣的 # 一對一 表一外來鍵關聯到表二,表一刪除,不影響表2,表2刪除會影響表1 # models.AuthorDetail.objects.get(id=2).delete() # models.Author.objects.get(id=3).delete() # 一對多 # models.Publish.objects.get(id=1).delete() # models.Book.objects.get(nid=1).delete() # 多對多關係刪除 # 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']) #刪除然後更新
更新
# 更新 # 一對一 # models.Author.objects.filter(id=5).update( # name='崔老師', # age=16, # # authorDetail=models.AuthorDetail.objects.get(id=5), # authorDetail_id=4, # ) #一對多 # models.Book.objects.filter(pk=4).update( # title='B哥的往事2', # # publishs=models.Publish.objects.get(id=3), # publishs_id=3, # ) #一對多 models.Publish.objects.filter(pk=2).update( id=4, # 沒有級聯更新,報錯!! )
正向查詢和反向查詢
關係屬性(欄位)寫在哪個類(表)裡面,從當前類(表)的資料去查詢它關聯類(表)的資料叫做正向查詢,反之叫做反向查詢
#查詢 # 一對一 # 正向查詢 #1 查詢崔老師的電話號 # author_obj = models.Author.objects.filter(name='崔老師').first() # # print(author_obj.authorDetail) #遼寧峨眉山 # # print(author_obj.authorDetail.telephone) #444 # #2 反向查詢 # #2 查詢一下這個444電話號是誰的. # author_detail_obj = models.AuthorDetail.objects.get(telephone='444') # print(author_detail_obj.author) #崔老師 # print(author_detail_obj.author.name) #崔老師 ''' 正向查詢:Authorobj.authorDetail,物件.關聯屬性名稱 Author----------------------------------->AuthorDetail <----------------------------------- 反向查詢:AuthorDetailobj.author ,物件.小寫類名 ''' # 一對多 # 查詢一下李帥的床頭故事這本書的出版社是哪個 # 正向查詢 book_obj = models.Book.objects.get(title='李帥的床頭故事') 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書 # 反向查詢 pub_obj = models.Publish.objects.get(name='B哥出版社') print(pub_obj.book_set.all()) #<QuerySet [<Book: 李帥的床頭故事>, <Book: 李帥的床頭故事2>]> ''' 正向查詢 book_obj.publishs 物件.屬性 Book ---------------------------------------------> Publish <---------------------------------------------- 反向查詢 publish_obj.book_set.all() 物件.表名小寫_set ''' # 多對多 # 李帥的床頭故事這本書是誰寫的 # 正向查詢 book_obj = models.Book.objects.get(title='李帥的床頭故事') print(book_obj.authors.all()) # 高傑寫了哪些書 author_obj = models.Author.objects.get(name='高傑') print(author_obj.book_set.all()) ''' 正向查詢 book_obj.authors.all() 物件.屬性 Book ---------------------------------------------> Author <---------------------------------------------- 反向查詢 author_obj.book_set.all() 物件.表名小寫_set '''
正向查詢和反向查詢
#查詢 # 一對一 # 1. 查詢崔老師的電話號 # 方式1 正向查詢 # obj = models.Author.objects.filter(name='崔老師').values('authorDetail__telephone') # print(obj) #<QuerySet [{'authorDetail__telephone': '444'}]> # 方式2 反向查詢 # obj = models.AuthorDetail.objects.filter(author__name='崔老師').values('telephone','author__age') # print(obj) #<QuerySet [{'telephone': '444'}]> # 2. 哪個老師的電話是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) # 一對多 # 查詢一下李帥的床頭故事這本書的出版社是哪個 # obj = models.Book.objects.filter(title='李帥的床頭故事').values('publishs__name') # print(obj) #<QuerySet [{'publishs__name': 'B哥出版社'}]> # obj = models.Publish.objects.filter(book__title='李帥的床頭故事').values('name') # obj = models.Publish.objects.filter(xx__title='李帥的床頭故事').values('name') # print(obj) # B哥出版社出版社出版了哪些書 # obj = models.Publish.objects.filter(name='B哥出版社').values('book__title') # print(obj) #<QuerySet [{'book__title': '李帥的床頭故事'}, {'book__title': '李帥的床頭故事2'}]> # obj = models.Book.objects.filter(publishs__name='B哥出版社').values('title') # print(obj) #<QuerySet [{'title': '李帥的床頭故事'}, {'title': '李帥的床頭故事2'}]> # 李帥的床頭故事這本書是誰寫的 # obj = models.Book.objects.filter(title='李帥的床頭故事').values('authors__name') # print(obj) # obj = models.Author.objects.filter(book__title='李帥的床頭故事').values('name') # print(obj) #<QuerySet [{'name': '高傑'}, {'name': '崔老師'}]> #高傑寫了哪些書 # obj = models.Book.objects.filter(authors__name='高傑').values('title') # print(obj) # obj = models.Author.objects.filter(name='高傑').values('book__title') # print(obj) #進階的 # B哥出版社 出版的書的名稱以及作者的名字 # obj = models.Book.objects.filter(publishs__name='B哥出版社').values('title','authors__name') # print(obj) #<QuerySet [{'title': '李帥的床頭故事', 'authors__name': '高傑'}, {'title': '李帥的床頭故事', 'authors__name': '崔老師'}, {'title': '李帥的床頭故事2', 'authors__name': '崔老師'},
{'title': '李帥的床頭故事2', 'authors__name': '王濤'}]> ''' 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 # 手機號以4開頭的作者出版過的所有書籍名稱以及出版社名稱 # ret = models.AuthorDetail.objects.filter(telephone__startswith='4').values('author__book__title','author__book__publishs__name') # print(ret) #QuerySet [{'author__book__title': '李帥的床頭故事', 'author__book__publishs__name': 'B哥出版社'}, {'author__book__title': '李帥的床頭故事2', 'author__book__publishs__name': 'B哥出版社'}]> #查詢一下B哥出版社出版了哪些書 # 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 # 計算所有圖書的平均價格 # obj = models.Book.objects.all().aggregate(a=Avg('price'),m=Max('price')) #aggregate()是QuerySet 的一個終止子句,得到的是個字典. # print(obj['m'] - 2) #{'price__avg': 2.833333}
分組
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查詢和Q查詢
from django.db.models import F,Q F 針對自己單表中欄位的比較和處理 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)) &優先順序高 filter(Q(Q(xx=11)|Q(ss=22))&Q(oo=33),name='dd')
執行原生sql(瞭解)
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)