ORM正向和反向查詢

表結構

from django.db import models

# create your models here.
class publisher(models.model):
id = models.autofield(primary_key=true)
name = models.charfield(max_length=32)
class book(models.model):
id = models.autofield(primary_key=true)
name = models.charfield(max_length=32)
publisher = models.foreignkey('publisher', related_name='person_book', related_query_name='ooxx')

插入資料

# book表

id   title  pubtime          person_id
1    書1    1533225600000    1
2    書2    1533225600000    1
3    書3    1534435200000    1
4    書4    1535644800000    2
5    書5    1535126400000    3

# publisher表

id   name    
1    出版社1    
2    出版社2    
3    出版社3

正向查詢： 外來鍵所在表去查另一張表，book >> publisher

反向查詢：普通表去查外來鍵所在的表，publisher >> book

正向查詢，基於物件跨表查詢

book_obj = models.book.objects.all()  # 取到書籍物件

book_obj.publisher.name   # 書籍的出版社名字，html
book_obj.person.id   # 書籍的出版社id，html

跨表查詢，利用雙下劃線跨表查詢

models.book.objects.filter(id=1).values('

publisher__name
')  # 查詢id是1的書的出版社的名字，一條雙下劃線就是跨一張表
models.book.objects.filter(id=1).values_list('publisher__name')

反向查詢

物件查詢  obj.表名_set()

publisher_obj =models.publisher.objects.first()  # 找到第乙個出版社物件

ret =publisher_obj.book_set.all()  # 找到第乙個出版社出版的所有數
for i in
ret:  # 迴圈物件
print(i.name)  # 列印出每乙個書的書名

publisher_obj = models.publisher.objects.first()  #

找到第乙個出版社物件
books = publisher_obj.book_set.all()  #
找到第乙個出版社出版的所有書
titles = books.values_list("
name
")  #
找到第乙個出版社出版的所有書的書名
print(titles)
因為使用了releted_name,就是用person_book代替了表字段名字
表字段person = models.foreignkey(person, related_name='person_book')
所以這一這樣寫
books = publisher_obj.person_book.all()
titles = books.values_list('name')
print(titles)
如果表字段person = models.foreignkey(person, related_name='person_book'，related_query_name="xxoo")
related_query_name="xxoo"，這裡表示跨表查詢xxoo代替表的名字book
books = publisher_obj.ooxx_set.all()

基於雙下劃線

ret = models.publisher.objects.filter(id=1).values_list('person_book__name')

person_book是通過releted_name給對應關係起的名字，通過person_book就找到了關聯的表，再通過雙下劃線找到name
print(ret)

附帶django裡面指令碼的**

import

osif
__name__ == '
__main__':
#載入django專案的配置資訊
os.environ.setdefault("
django_settings_module
", "
專案名.settings")
#匯入django，並啟動django專案
import
django
django.setup()
models
# 查詢id為1的出版社出版的所有書的name
ret = models.publisher.objects.filter(id=1).values_list('
person_book__name')
print(ret)

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