and check* operations on the database in Django

Foreword What is an ORM? ORM (Object Relational Mapping) refers to using object-oriented methods to handle operations such as creating tables in the database and adding, deleting, modifying, and querying data. A table in the database = a class. Each record in the database = an object. In short, defining a class in Django is to create a table in the database. Instantiating an object of a class in Django adds a record to the database. Deleting an object in Django deletes a record in the database. Changing the properties of an object in DJango is to modify the value of a record in the database. Traversing the attribute values ​​of the query object in Django is to query the value of the record in the database. The following are several command statements in Django’s views function. One, increase (create, save) from app01.models import * #Create method one: Author.objects.create(name=\’Alvin\’) #Create method two: Author.objects.create(**{“name”:”alex”}) #save method one: author=Author(name=”alvin”) author.save() #Save method two: author=Author() author.name=”alvin” author.save() Two, delete >>> Book.objects.filter(id=1).delete() (3, {\’app01.Book_authors\’: 2, ​​\’app01.Book\’: 1}) If it is a many-to-many relationship: remove() and clear() methods: #Forward book = models.Book.objects.filter(id=1) #Delete all related information associated with girl 1 in the third table book.author.clear()…