Django Database Operations-additions and deletions-many-to-many relationships and one-to-many (foreign key) relationships

Django Database Operations-additions and deletions-many-to-many relationships and one-to-many (foreign key) relationshipsoriginal August 29, 2012 14:56:33

• Label:
• Django/
• Database
• Class/
• Email/
• Publishing

• 28343

One or one-to-many (foreign key)

Example: One author corresponds to multiple books, one book only one author

Model Code:

[Python]View Plain Copy

1. Class person (models. Model);
2. Name = models. Charfield (' author name ', max_length=)
3. Age = Models. Integerfield (' author age ')
5. Class book (Models. Model):
6. Person = models. ForeignKey (person, related_name=' Person_book ')
7. title = models. Charfield (' book name ', max_length=)
8. Pubtime = models. Datefield (' publication Time ')

(i) Get the object method:

1. Obtaining books from the author

[python] view plain copy

1. person = Person.objects.fiter (your condition)
2. Book = Person.book_set.all ()

2. Get authors from books

[python] view plain copy

1. p = Book.person

Two, many-to-many

Example: One author corresponds to multiple books, one book has multiple authors

Model Code:

[Python]View Plain Copy

1. Class Author (models. Model):
2. First_Name = models. Charfield (max_length=)
3. Last_Name = models. Charfield (max_length=)
4. email = models. Emailfield ()
6. Class book (Models. Model):
7. title = models. Charfield (max_length=)
8. Authors = models. Manytomanyfield (Author)

(i) Get the object method:

1. Get authors from books

[python] view plain copy

1. b = Book.objects.get (id=)
2. B.authors.all ()
3. B.authors.filter (first_name=' Adam ')

2. Obtaining books from the author

[python] view plain copy

1. A = Author.objects.get (id=1)
2. A.book_set.all ()

(ii) Add object method:

[Python]View Plain Copy

1. A = Author.objects.get (id=1)
2. b = Book.objects.get (id=)
3. B.authors.add (a)

(iii) Delete Object object methods:

[Python]View Plain Copy

1. A = Author.objects.get (id=1)
2. b = Book.objects.get (id=)
3. B.authors.remove (a) or B.authors.filter (id=1). Delete ()

Django Database Operations-additions and deletions-many-to-many relationships and one-to-many (foreign key) relationships