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')

# book表

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

# publisher表

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

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

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')

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()

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)

import os

if __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()
# 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)

ORM正向和反向查詢

表結構 from django.db import models class publisher models.model id models.autofield primary key true name models.charfield max length 32 class book mode...

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 l...

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