Cross-table query
A, ORM cross-table query
class Book(models.Model):
title = models.CharField(max_length=32)
publish = models.ForeignKey(to="Publish",to_field="id",on_delete=models.CASCADE)
authors = models.ManyToManyField(to = "Author",related_name='bookList')
class Publish(models.Model):
name = models.CharField(max_length=32)
class Author(models.Model):
name = models.CharField(max_length=32)
ad = models.OneToOneField("AuthorDetail",on_delete=models.CASCADE)
class AuthorDetail(models.Model):
telephone = models.BigIntegerField()
1, based on an object query (sql: sub-query) :
Many, (Publish - Book)
Forward query by field: Query python name of the book publishing house where book_obj = Book.objects.filter (title = "python") First (). Print (book_obj.publish.name) reverse lookup, according to show lowercase _set: People's Publishing House published the names of all books publish_obj = Publish.objects.filter (name = "People's Publishing House") .first () Print (publish_obj.book_set.all ()) for obj in publish_obj.book_set. All (): Print (obj.title) displayed one title
Many to many,
Forward query by field: Python book all authors' names book_obj = Book.objects.filter (title = "Python") First (). Book_obj.authors.all () reverse lookup, according to show lowercase _set: alex all the books ever published name alex = Author.objects.filter (name = "alex ") first (). method one: alex.book_set.all () method II (which is set related_name = 'bookList' method): alex .bookList.all ()
One on one,
Forward query by field: Query phone number alex alex = Author.objects.filter (name = "alex") First (). Alex.ad.telephone reverse lookup, according to show lowercase: beginning with 151 phone numbers the author's name AD = AuthorDetail.objects.get (telephone__startswith = "151") ad.authour.name
2, based on Queryset and __ (sql: join statement):
Forward query by field
reverse lookup, according to show lowercase
-to-many, (Publish - Book)
forward query by field:
Query python book publishing house where the name
Book.objects.filter (title = "python ") .values (" publish__name ")
for obj in Book.objects.filter (title =" Python "):
the TEMP = {}
the TEMP [" publish__name "] = obj.publish.name
reverse lookup, according to show lowercase:
people Press published the names of all the books
Publish.objects.filter (name = "People's Publishing House") .values ( "book__title")
many to many,
Python book all authors' names
Book.objects.filter (title = . "Python") values ( "authors__name")
alex all the books ever published names
. Author.objects.filter (name = "alex" ) values ( "book__title")
one on one,
forward query by field:
query alex phone number
Author.objects.filter (name = "alex") . values ( "ad__telephone")
to 151 at the beginning of the phone number of the author's name
AuthorDetail.objects.filter(telephone__startswith="151").values("author__name")
Third, expand
eg1: Query python book publishing house where the name Book.objects.filter (title = "python") values ( "publish__name"). Publish.objects.filter (book__title = "python") values ( "name"). eg2: the author's name phone number beginning with 151 . AuthorDetail.objects.filter (telephone__startswith = "151") values ( "author__name") Book.objects.filter (authors__ad__telephone__startswith = "151") values ( "title",. "publish__name")