The Django Book - Chapter 5: Models
- 1. The Django Book—Models Sharre Chen http://django-book.readthedocs.org/en/latest/index.html
- 2. The “Dumb” Way to Do Database Queries in Views
- 4. MVC M(Model): data access logic, is handled by Django’s database layer V(View): business logic, is handled by views and templates. C(Controller): presentation logic, is handled by the framework itself by following your URLconf and calling the appropriate Python function.
- 5. MTV M(Model): data access layer. T(Template): the presentation layer. V(View): business logic layer.
- 6. Configuring the Database • In settings.py: Example for MySQL: DATABASE_ENGINE = 'mysql' DATABASE_NAME = 'mydb' DATABASE_USER= 'user' DATABASE_PASSWORD = 'password' DATABASE_HOST = ‘/var/run/mysql' ! Try if setting is correct: $ python manage.py shell >>> from django.db import connection >>> cursor = connection.cursor()
- 7. What’s the difference between a project and an app? • A project is an instance of a certain set of Django apps, plus the configuration for those apps. • An app is a portable set of Django functionality, usually including models and views, that lives together in a single Python package. ★if you’re using Django’s database layer (models), you must create a Django app.
- 8. Create an app create a books app: $ python manage.py startapp books file structure will look like:
- 9. Data access with Django
- 10. Installing the Model Edit setting.py file again: ! ! ! !
- 11. Check models’ syntax checks whether your models’ syntax and logic are correct: $ python manage.py validate
- 12. check create table sql If your models are valid, run the following command for Django to generate CREATE TABLE statements for your models in the books app (before migration): $ python manage.py sqlall books
- 13. commit the SQL to database $ python manage.py syncdb ! ! ★ Note that syncdb does not sync changes in models or deletions of models.
- 14. Basic data access Try it out: $ python manage.py shell
- 15. Basic data access If you want to create an object and save it to the database in a single step, use the objects.create() method.
- 16. Adding Model String Representations it difficult to tell the Publisher objects apart:
- 17. Inserting and Updating Data update name: will result in:
- 18. Selecting Objects if you type command: This roughly translates to this SQL: ! ✦ Zen of Python: “Explicit is better than implicit.”
- 19. Filtering Data filter data: This roughly translates to this SQL: !
- 20. Filtering Data: LIKE filter data: ! here, the __contains part gets translated by Django into a SQL LIKE statement: !
- 21. Retrieving Single Objects get single data: will result in: ! ! you may write:
- 22. Ordering Data get ordered data: SQL will be: ! To order by multiple fields: ! specify reverse ordering:
- 23. Ordering Data Specify a default ordering in model:
- 24. Chaining Lookups get filtered and ordered data: ! As SQL:
- 25. Slicing Data get first ordered data: ! As SQL:
- 26. Slicing Data but can not do: ! ! you can do in another way:
- 27. Updating Multiple Objects in One Statement update a filed: ! ! update will return success updated object number:
- 28. Deleting Objects delete a data: ! ! delete all matched data:
- 29. Q&A Thank You ~ :)