The path to learning in Python -2018/6/26

The path to learning in Python -2018/6/26 1.ORM Single-table operation delete and modify records

>>> ret = Book.objects.filter(title="go").delete()(1, {‘app01.Book‘: 1})>>> Book.objects.filter(price=115).update(price=120)

Multiple table operations Create a model

One

models.OneToOneField(to="表名", on_delete=models.CASCADE)

One-to-many

models.ForeignKey(to="表名", to_field="字段名", on_delete=models.CASCADE)

Many-to-many

models.ManyToManyField(to="表名")

models.py

 fromDjango.dbImportModelsclassAuthor (models. Model): Nid=Models. Autofield (Primary_key=True) name=Models. Charfield (max_length= +) Age=Models. Integerfield ()# Establish a one-to-one relationship with AuthordetailAuthor_detail=Models. Onetoonefield (To="Authordetail", On_delete=Models. CASCADE)classAuthordetail (models. Model): Aid=Models. Autofield (Primary_key=True) Birthday=Models. Datefield () Telephone=Models. Bigintegerfield () addr=Models. Charfield (max_length= -)classPublish (models. Model): PID=Models. Autofield (Primary_key=True) name=Models. Charfield (max_length= +) City=Models. Charfield (max_length= +) Email=Models. Emailfield ()classBook (Models. Model): Bid=Models. Autofield (Primary_key=True) title=Models. Charfield (max_length= +) publishdate=Models. Datefield () Price=Models. Decimalfield (max_digits=5, decimal_places=2)# Establish a one-to-many relationship with publish, and foreign key fields are built on more than one sidePublish=Models. ForeignKey (To="Publish", To_field="pid", On_delete=Models. CASCADE)"""publish_id INT,FOREIGN KEY (publish_id) REFERENCES publish (PID)    """    # Establish Many-to-many relationships with authorAuthors=Models. Manytomanyfield (To="Author")"""CREATE TABLE Book_author (ID INT PRIMARY KEY auto_increment,book_id INT,author_id INT,FOREIGN KEY (book_id) REFERENCES book (BID),FOREIGN KEY (author_id) REFERENCES author (nid),        )    """

Operation Result:

Attention:

• On_delete = models. Cascade use a pair and a couple of
• The foreign key field will automatically add _id, such as Publish = models. ForeignKey () generates publish_id after execution
• Need to configure APP01 in settings.py

Add a record

One-to-many

Book.objects.create(title="坏蛋是怎样炼成的", publishDate="2017-01-02", price=125, publish_id=1)

Operation Result:

>>>  book =  Book.objects.get (Bid=  1 )  >>>  print  (book.bid) 1  >>  print  (Book.title) How the villain is refined >>>  print  (book.publishdate) 2017-01-02  >>>  print  (Book.price) 125.00  >>>  print  (Book.publish) Publish object  (1 ) >>>  print  (book.publish.name) China City Press >>>  print  (book.publish.email ) [email protected]  

Python Learning Path -2018/6/26